Download annual report 2014 - Department of Applied Physics

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ANNUAL REPORT
2014
Aalto University
School of Science
O.V. Lounasmaa Laboratory
http://ovll.aalto.fi
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Table of Contents
PREFACE ..................................................................................................................... 4 SCIENTIFIC ADVISORY BOARDS .......................................................................... 6 PERSONNEL ................................................................................................................ 6 ADMINISTRATION AND TECHNICAL PERSONNEL ....................................... 6 RESEARCH PERSONNEL ...................................................................................... 7 VISITORS ............................................................................................................... 10 EUROPEAN RESEARCH PROJECTS...................................................................... 13 Participation in the Flagship projects of EU ........................................................... 13 Other European projects .......................................................................................... 13 SEMINARS AND WORKSHOPS ............................................................................. 16 Kopnin symposium ................................................................................................. 16 Voiko aivotutkija lukea mieltäsi? ............................................................................ 16 Workshop on flat bands and room-temperature superconductivity ........................ 16 5th Graphene and 2D Materials Satellite Symposium (GSS14) .............................. 16 Aivot ja mieli, käsitteet ja kieli ............................................................................... 17 3rd BRAHE symposium ........................................................................................... 17 TMS-fMRI Workshop 2014 .................................................................................... 17 Aivokummien teemailtapäivä.................................................................................. 17 LOW TEMPERATURE PHYSICS RESEARCH ...................................................... 19 KVANTTI group ..................................................................................................... 19 NANO group ........................................................................................................... 21 NEMS group ........................................................................................................... 32 PICO group ............................................................................................................. 35 ROTA group ............................................................................................................ 47 µKI group ................................................................................................................ 53 THEORY group ...................................................................................................... 56 BRAIN RESEARCH UNIT ........................................................................................ 64 ATTENTION AND MEMORY.............................................................................. 67 CliniMEG ................................................................................................................ 71 HUMAN SYSTEMS NEUROSCIENCE ............................................................... 72 IMAGING LANGUAGE ........................................................................................ 83 TEACHING ACTIVITIES.......................................................................................... 92 COURSES IN LOW TEMPERATURE AND NANOPHYSICS ........................... 92 COURSES IN BRAIN RESEARCH ...................................................................... 92 Annual Report 2014
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RESEARCH SEMINARS IN LOW TEMPERATURE PHYSICS AND
NANOPHYSICS ..................................................................................................... 92 BRAIN RESEARCH SEMINARS ......................................................................... 95 SPECIAL ASSIGNMENTS .................................................................................... 98 ACADEMIC DEGREES......................................................................................... 98 PH.D. DISSERTATIONS ....................................................................................... 99 TECHNICAL SERVICES ........................................................................................ 100 CRYOGENIC LIQUIDS....................................................................................... 100 MACHINE SHOP ................................................................................................. 100 ACTIVITIES OF THE PERSONNEL ...................................................................... 102 PUBLICATIONS ...................................................................................................... 125 Annual Report 2014
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PREFACE
O.V. Lounasmaa Laboratory (OVLL), founded in 1965, is an interdisciplinary unit in
Aalto School of Science (SCI). It is comprised of the Low Temperature Laboratory
(LTL) and the Brain Research Unit (BRU). The main research fields of LTL are lowtemperature quantum electronics and ultra-low temperature physics, whereas the research of BRU focuses on systems-level neuroscience and human brain imaging.
Year 2014 was a year of changes for the laboratory. Adjunct professor Matti Hämäläinen from Harvard was nominated as a full professor in Systems neuroscience, and
the assimilation of his research group Multimodal Neuroimaging, Signal Analysis, and
Modeling to the BRU was started. Dr. Christian Flindt (University of Geneva) was
appointed to the Aalto tenure track professorship in Theoretical condensed matter
physics of quantum phenomena and devices, to work first part time and then fully
starting 1st of Feb. 2015. Another position for Aalto tenure track professor in Experimental quantum physics was opened in association with the Department of Applied
Physics. The leader of the ROTA group, Dr. Vladimir Eltsov, received the title of docent in topological materials and was later on appointed to a senior scientist position
related to the Low Temperature Laboratory infrastructure. Dr. Matthias Meschke received the title of docent in nanotechnology of quantum devices, and was appointed to
a senior scientist position related to the Low Temperature Laboratory and Aalto
Nanofab infrastructures.
State-of-the-art research infrastructures are a solid basis for the world-renowned work
of the research groups of the laboratory. In 2014, the Aalto NeuroImaging (ANI) and
the Low Temperature Laboratory (LTL) research environments administered and developed by OVLL were selected to Finland's strategy and roadmap for research infrastructures 2014–2020: LTL as part of Otaniemi Research Infrastructure for Microand Nanotechnologies (OtaNano), and ANI as part of the prospective Finnish node in
Euro-BioImaging (ESFRI), coordinated by Åbo Akademi University (vice-coordinator
is Academy Professor Riitta Salmelin).
The scientific quality and societal impact of our research was recognized in multiple
ways. Professor Claudia Tesche, a long-time OVLL collaborator, was awarded an
Honorary Doctorate in October 2014. The founder of the LTL spin-off company
BlueFors Cryogenics, Dr. Rob Blaauwgeers, was nominated as the first ever Alumnus
of the Year of the Aalto School of Science. To boost the scientific collaboration and
to maximize the impact of our research, two strategic initiatives were pushed forward.
Aalto Brain Centre (ABC), a multidisciplinary thematic center in neuroscience and
neurotechnology started with full speed in June 2014 with the support of the Aalto
School of Science. At the end of 2014, Aalto Centre for Quantum Engineering (CQE)
received green light and seed-funding from the Aalto School of Science, enabling
CQE to be ramped up in the first half of 2015.
During 2014 the activities of the Aalto School of Science were reviewed by the
School’s Scientific Advisory Board. The outcome of the review led to rapid changes
in the departmental structure. We merely had a chance to celebrate our 50-year history, whilst from the beginning of 2015, LTL became a part of the new Department of
Applied Physics and the BRU formed a new Department of Neuroscience and Biomedical Engineering together with the former Department of Biomedical Engineering
and Computational Science.
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I am grateful to all members of our staff for the high spirits of this laboratory and the
feeling of familial togetherness. It is now up to us all to take care that the new affiliations will generate increased amount of synergy, and thereby impact positively on our
research. I strongly believe that the road ahead will help us to raise the future level of
physics and neuroscience in Aalto and, at the same time, it will lead to abundant rewards, some of which will be unexpected as so many results in science.
Pertti Hakonen
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SCIENTIFIC ADVISORY BOARDS
SAB for aivoAALTO:
Prof. Olivier Bertrand, Lyon Neuroscience Research Center, France
Prof. Torben Grodal, University of Copenhagen, Denmark
Prof. Rosemarie Nagel, Universitat Pompeu Fabra, Barcelona, Spain
SAB for the Center of Excellence on Low Temperature Quantum Phenomena and Devices:
Prof. William Halperin, Northwestern University, Evanston, Illinois, USA
Prof. Andrew Cleland, University of California, USA
Prof. Milena Grifoni, Universität Regensburg, Germany (October 2014 -->)
PERSONNEL
The number of persons working in the OVLL fluctuates considerably since scientists
are employed for fixed periods and students often work on part-time basis.
ADMINISTRATION AND TECHNICAL PERSONNEL
Minna Günes, Ph.D., coordinator
Teija Halme, secretary
Mia Illman, biomedical laboratory technologist (clinical neurophysiology)
Jari Isomäki, technician
Olga Jakkola, HR secretary until 30.9.2014
Eeva Käki, HR secretary starting 27.10.2014
Mari Kaarni, HR coordinator
Helge Kainulainen, technician
Marita Kattelus, radiographer (AMI)
Karel Kaurila, non-military service until 14.8.2014
Markku Korhonen, technician
Jenny Kotiranta, secretary
Jussi Nurminen, M.Sc. (Tech.), project engineer until 30.6.2014
Kirsi Romanoff, project-planning officer until 30.9.2014
Emilia Korpelainen, secretary
Petteri Räisänen, system administrator
Veli-Matti Saarinen, project engineer
Joel Salminen, technician, from 20.6.2014
Alexander Savin, Ph.D., staff scientist
Ronny Schreiber, research engineer
Katariina Toivonen, controller
Tuomas Tolvanen, M.Sc., technical assistant
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RESEARCH PERSONNEL
SENIOR RESEARCHERS
Low Temperature Laboratory
Massimo Borrelli, Ph.D., from 1.5.2014
Vladimir Eltsov, Ph.D., Docent
Dmitry Golubev, Ph.D.
Pertti Hakonen, D.Sc. (Tech.), Professor, Director of the OVLL
Tero Heikkilä, D.Sc. (Tech.), Docent, Visiting Professor until 30.6.2014
Risto Hänninen, D.Sc. (Tech.) Academy Research Fellow
Ivan Khaymovich, Ph.D.
Matti Krusius, D.Sc. (Tech.), Professor, Emeritus
Manohar Kumar, Ph.D.
Jian Li, Ph.D. (Tech) until 31.7.2014
Matthias Meschke, Ph.D., Docent
Hung Nguyen, Ph.D.
Caspar Ockeloen, Ph.D., from 1.8.2014
Teemu Ojanen, Ph.D.
Gheorghe-Sorin Paraoanu, Ph.D., Docent
Jukka Pekola, D.Sc. (Tech.), Academy Professor
Joonas Peltonen, Ph.D., from 1.4.2014
Juha-Matti Pirkkalainen, Ph.D., from 1.4.2014
Olli-Pentti Saira, Ph.D., from 1.2.2014
Alexander Sebedash, Ph.D.
Mihkail Silaev, Ph.D., until 31.7.2014
Xuefeng Song, Ph.D.
Zhenbing Tan, Ph.D. (Tech.)
Mathieu Taupin, Ph.D., from 1.3.2014
Igor Todoschenko, Ph.D.
Juha Tuoriniemi, D.Sc. (Tech.), Docent
Pauli Virtanen, Ph.D.
Grigori Volovik, Ph.D., Professor
Vladislav Zavyalov, Ph.D.
Brain Research Unit
Riitta Hari, M.D., Ph.D., Academy Professor, Academician, Head of the Brain Research Unit
Toni Auranen, D.Sc. (Tech.)
Mathieu Bourguignon, Ph.D.
Synnöve Carlson, M.D., Ph.D., Professor of Practice
Ali Faisal, Ph.D.
Nina Forss, M.D., Ph.D., Docent
Hanna Heikkinen, D.Sc. (Tech.)
Linda Henriksson, D.Sc. (Tech.)
Tommi Himberg, Ph.D.
Kaisa Hytönen, Ph.D. until 31.5.2014
Annika Hulten, Ph.D.
Veikko Jousmäki, Ph.D., Docent
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Jukka-Pekka Kauppi, Ph.D. until 31.5.2014
Sasa Kivisaari, Ph.D., from 7.1.2014
Miika Koskinen, D.Sc. (Tech.)
Jan Kujala, D.Sc. (Tech.)
Hannu Laaksonen, D.Sc. (Tech.)
Mia Liljeström, D.Sc. (Tech.)
Tiina Lindh-Knuutila, Ph.D. from 1.3.2014
Sanna Malinen, D.Sc. (Tech.) until 31.5.2014
Mathilde Ménoret, Ph.D. from 6.1.2014
Harri Piitulainen, Ph.D.
Elina Pihko, Ph.D., Docent
Tuukka Raij, M.D., Ph.D.
Hanna Renvall, M.D., Ph.D.
Ville Renvall, D.Sc. (Tech.)
Riitta Salmelin, D.Sc. (Tech.), Academy Professor
Jaeho Seol, Ph.D.
Mika Seppä, D.Sc. (Tech.) until 18.5.2014
Kevin Tsai, Ph.D.
Guanguy Zhou, Ph.D.
GRADUATE STUDENTS – (SUPERVISORS)
Low Temperature Laboratory
Samuli Autti, M.Sc. – (Vladimir Eltsov)
Daniel Cox, M.Sc. – (Pertti Hakonen)
Sergey Danilin, M.Sc. – (Gheorghe-Sorin Paraoanu)
Timothé Faivre, M.Sc. – (Jukka Pekola)
Anna Feshchenko, M.Sc. – (Jukka Pekola)
Simone Gasparinetti, M.Sc. – (Jukka Pekola) until 30.6.2014
Petri Heikkinen, M.Sc. (Tech.) – (Vladimir Eltsov)
Niklas Hietala, M.Sc. – (Risto Hänninen)
Pasi Häkkinen, M.Sc. –(Pertti Hakonen) from 16.4.2014
Jukka-Pekka Kaikkonen, M.Sc. – (Pertti Hakonen)
Ville Kauppila, M.Sc. (Tech.) – (Tero Heikkilä)
Raphaël Khan, M.Sc. (Tech.) – (Tero Heikkilä)
Jonne Koski, M.Sc. – (Jukka Pekola)
Antti Laitinen, M.Sc. – (Pertti Hakonen) from 1.10.2014
Pasi Lähteenmäki, M.Sc. (Tech.) – (Pertti Hakonen)
Ville Maisi, M.Sc. (Tech.) – (Jukka Pekola, Antti Manninen) until 30.4.2014
Matti Manninen, M.Sc. (Tech.) – (Juha Tuoriniemi)
Robab Najafi Jabdaraghi, M.Sc. (Tech.) – (Jukka Pekola)
Mika Oksanen, M.Sc. – (Pertti Hakonen)
Juha-Matti Pirkkalainen, M.Sc. (Tech.) – (Mika Sillanpää) until 31.3.2014
Antti Puska, M.Sc. (Tech.) – (Pertti Hakonen)
Joel Röntynen, M.Sc. (Tech.) – (Teemu Ojanen) until 30.6.2014
Karthikeyan Sampath Kumar, M.Sc. – (Gheorghe-Sorin Paraoanu)
Jayanta Sarkar, M.Sc. – (Pertti Hakonen) until 31.3.2014
Shilpi Singh, M.Sc. – (Jukka Pekola) from 8.9.2014
Antti Vepsäläinen, M.Sc. – (Gheorghe-Sorin Paraoanu) from 1.10.2014
Klaara Viisanen, M.Sc. – (Jukka Pekola)
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Brain Research Unit
Heidi Ala-Salomäki, M.Sc. – (Riitta Salmelin) from 1.7.2014
Anna Maria Alexandrou, M.Sc. – (Riitta Salmelin)
Anna-Maria Bique, M.Sc. – (Juha Silvanto) until 6.3.2014
Robert Boldt, M.D. – (Synnöve Carlson) until 30.6.2014
Silvia Bona, M.D. – (Juha Silvanto)
Zuyue Chen, M.Sc. – (Synnöve Carlson) from 1.4.2014
Tero Hakala, M.Sc. – (Riitta Salmelin) from 3.2.2014
Lotta Hirvenkari, M.Sc. (Biol.) – (Riitta Hari, Veikko Jousmäki) on leave from
21.3.2014
Jaakko Hotta, M.D. – (Nina Forss, Riitta Hari)
Kaisu Lankinen, M.Sc. (Tech.) – (Riitta Hari, Instructor: Miika Koskinen)
Anne Mandel, M.Sc. (Psychol. & Neurosci.) – (Riitta Hari)
Teemu Mäntylä, M.A. (Psychol.) – (Tuukka Raij)
Anni Nora, M.A. (Psychol.) – (Riitta Salmelin)
Siina Pamilo, M.Sc. – (Riitta Hari)
Eeva Parkkonen, M.D., neurologist – (Nina Forss)
Riikka Rajamäki, M.D. – (Nina Forss) from 1.8.2014
Elyana Saad, M.Sc. – (Juha Silvanto)
Jukka Saari, M.Sc. – (Miika Koskinen, Riitta Hari)
Fariba Sharifian, M.Sc. – (Simo Vanni)
Eero Smeds, M.D. – (Riitta Hari, Lauri Parkkonen)
Maksym Tokariev, M.Sc. – (Synnöve Carlson)
UNDERGRADUATE STUDENTS
Low Temperature Laboratory
Erno Damskägg
Miika Haataja from 1.6.2014 until 31.8.2014
Pasi Häkkinen until 14.4.2014
Olli Ihalainen until 31.8.2014
Jesper Ilves from 28.4.2014 until 31.8.2014
Timo Kamppinen
Antti Laitinen until 30.9.2014
Jori Lemettinen from 6.5.2014 until 31.8.2014
Elsa Mannila
Antti Moisio from 19.5.2014
Jere Mäkinen
Teemu Nieminen
Topi Paananen from 19.5.2014
Taneli Prittinen until 10.8.2014
Kim Pöyhönen from 1.6.2014
Antti Ranni from 19.5.2014 until 31.8.2014
Antti Rantala
Tapio Riekki
Ilmo Räisänen from 2.6.2014
Slawomir Simbierowicz from 19.5.2014 until 31.8.2014
Ari-Pekka Soikkeli from 1.6.2014
Aapo Taavitsainen from 1.6.2014 until 31.8.2014
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Matti Tomi
Antti Vepsäläinen until 30.9.2014
Alex Westström from 1.6.2014
Klaara Viisanen until 31.3.2014
Brain Research Unit
Miro Hakonen
Laura Jukola from 1.6.2014 until 31.8.2014
Tomi Karjalainen until 31.5.2014
Crista Kaukinen from 26.5.2014 until 29.8.2014
Karel Kaurila from 15.8.2014
Janne Laitinen from 26.5.2014 until 31.8.2014
Pekka Laitio from 26.5.2014
Lotta Lammi from 28.5.2014
Sasu Mäkelä from 28.5.2013
Magdalena Navarro from 2.6.2014 until 29.8.2014
Maija Niinisalo
Timo Nurmi from 5.5.2014 until 31.12.2014
Karita Ojala until 31.5.2014
Elias Raninen from 26.5.2014
Timo Saarinen
Kerttu Seppälä until 21.12.2014
Abdul Hadi Shakir from 14.5.2014 until 10.8.2014
Manish Kumar Sharma from 5.5.2014 until 11.7.2014
Emma Suppanen until 31.5.2014
Taneli Vuornos until 31.7.2014
Rasmus Zetter from 13.5.2014
Kaisu Ölander from 22.5.2014
VISITORS
LOW TEMPERATURE LABORATORY VISITORS
Ankerhold, Joachim, Prof., 24.3. – 18.4., Ulm University, Germany
Arutyunov, Konstantin, Dr.Sci., 11. – 12.3., University of Jyväskylä, Finland
Arzeo, Marco, M.Sc., 12.1. – 8.2., Chalmers University of Technology, Sweden
Attila, Geresdi, M.Sc., 14. – 17.10., Budapest University of Technology and Economics, Hungary
Brunetti, Adalberto, Ph.D., 23. – 25.3., University of Bari, Italy
Bu, Shirong, Ph.D., 3.11. – 31.12., University of Electronic Science and Technology
of China, China
Campisi, Michele, Ph.D., 21.7. – 1.8., Scuola Normale Superiore, Italy
Charles, Marcus, Prof., 14.5., University of Copenhagen, Denmark
Cleland, Andrew, Prof., 19. – 23.1., University of California, USA
Dasenbrook, David, 20. – 24.10., University of Geneva, Switzerland
Dmitriev, Vladimir, Dr.Sci., 20. – 27.1., Kapiza institute for physical problems RAS,
Russia
Dutta, Bivas, M.Sc., 15. – 17.12., Indian Institute of Technology, Kanpur, India
Esquinazi, Pablo, Prof., 29.5. – 1.6., University of Leipzig, Germany
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Fazio, Rosario, Prof., 24. – 28.3., Scuola Normale Superiore, Italy
Flindt, Christian, Ph.D., 22. – 26.9. and 20.-24.10., University of Geneva, Switzerland
Galperin, Yuri, Prof. Emeritus, 23. – 25.1., University of Oslo, Norway
Halperin, William, Prof., 19. – 21.1., Northwestern University, Evanston, Illinois,
USA
Haviland, David, Prof., 18. – 19.11., KTH Royal Institute of Technology, Sweden
Hekking, Frank, Prof., 24. – 27.5., Centre national de la recherché scientifique,
CNRS, France
Isacsson, Andreas, Assoc. Prof., 20. – 31.1. and 14.-18.4., Chalmers University of
Technology, Sweden
Jannes, Gil, Ph.D., 14. – 18.7., Universidad Carlos III de Madrid, Spain
Khodel, Victor, Adjunct. Prof., 29.5. – 1.6., Washington University in St. Louis, USA
Kopnina, Helen, Ph.D., 23. – 25.1., Hague University of Applied Sciences, Netherlands
Lesovik, Gordey, Dr. Sci., 20.10. – 7.11., Landau Institute for Theoretical Physics
RAS, Russia
Li, Chuan, Ph.D., 19. – 21.5., University of south Paris, France
Matsuura, Toru, Assistant Prof., 24. – 27.8., Hokkaido University, Japan
Mel'nikov, Alexander, Dr.f., 9. – 30.1. and 24.10. –21.11., Institute for physics of microstructures RAS, Russia
Mineev, Vladimir, Dr.Sci., 22. – 25.1., Institute of Nanosciences and Cryogenics CEA, France
Nagaev, Kirill, Prof., 6. – 11.10., Institute of Radioengineering and Electronics, RAS,
Russia
Nakahara, Mikio, Prof., 13. – 16.3., Kinki University, Japan
Nakamura, Shuji, Dr., 11.11. – 31.12., National Institute of Advanced Industrial Science and Technology, Japan
Nobukane, Hiroyoshi, Assistant Prof., 11. – 13.8. and 24. – 27.8., Hokkaido University, Japan
Placais, Bernard, Prof., 6.4. – 3.5., HDR, École Normale Supérieure, France
Polzik, Eugene, Prof., 10. – 13.4., University of Copenhagen, Denmark
Porthier, Hugues, Prof., 30.4. – 2.5., French Alternative Energies and Atomic Energy
Commission, France
Santos, Jorge, Prof., 11. – 14.3., INESC Microsistemas e Nanotecnologias, Portugal
Semenov, Adrew, Ph.D., 9. – 22.3., Lebedev Physical Institute, RAS, Russia
Sonin, Edouard, Prof., 21. – 28.9., Hebrew University of Jerusalem, Israel
Staudt, Matthias, Ph.D., 15. – 18.3., Friedrich-Alexander-Universität ErlangenNürnberg, Germany
Tanda, Satoshi, Prof., ., 11. – 13.8. and 24. – 27.8., Hokkaido University, Japan
Tayurskii, Dmitrii, Prof., 29.5. – 1.6., Kazan University, Russia
Utsumi, Yasuhiro, Prof., 26.4. – 3.5., Mie University, Japan
van Zanten, David, M.Sc., 20. – 22.7., Institute Neel, France
Zaikin, Andrei, Dr., 10. – 11.3., Karlsruhe Institute of Technology/ Institute of Nanotechnology, Germany
Zgirski, Maciej, Dr., 13.7. – 21.12., Institute of Physics, Polish Academy of Sciences,
Poland
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BRAIN RESEARCH UNIT VISITORS
Boujut, Hugo, Ph.D., 15. – 30.3., Institut Mines-Telecom-SudParis, France
Chitose, Ryota, B.Sc., 2. – 15.9., Hokkaido University, Japan
Dinh, Christoph, M.Sc., 12. – 24.10., MGH/HST Athinoula A. Martinos Center for
Biomedica Imaging, USA
Esch, Lorenz, M.Sc., 12. – 24.10., TU Ilmenau, Germany
Evans, John, Ph.D., 29. – 31.10., Cardiff University, UK
Feredoes, Eva, Ph.D., 29.10. – 1.11., University of Reading, UK
Giese, Martin, Prof., 8. – 10.4., University of Tübingen, Germany
Hincapie Casas, Ana Sofia, M.Sc., 16. – 26.5., Lyon Neuroscience Research Center
Liu, Qingzi, B.Sc., 2. – 15.9., Hokkaido University, Japan
Ma, Yuan-Ye, Prof., 1. – 27.6., Kunming Institute of Zoology, CAS, China
Murakami, Yui, M.Sc., 2. – 15.9., Hokkaido University, Japan
Navarro Torres, Magdalena, 1.6. – 20.10., Instituto Technologico, Anto Nomo de
Mexico ITAM, Mexico
Nobre, Kia, Prof., 6. – 8.3., University of Oxford, UK
Peled, Noam, Ph.D., 12. – 18.10., Bar Ilan University, Israel
Riecke, Lars, Ph.D., 5.6., Maastricht University, Netherlands
Ruff, Christian, Prof., 29. – 31.10., University of Zurich, Switzerland
Schürmann Martin, Assoc. Prof., 17. – 19.12., Nottingham University, UK
Sorger, Bettina, Assistant Prof., 5.6., Maastricht University, Netherlands
van Vliet, Marijn, M.Sc., 4.10. – 31.12., KULeuven, Belgium
Yokosawa, Koichi, Prof., 2. – 15.9., Hokkaido University, Japan
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EUROPEAN RESEARCH PROJECTS
Participation in the Flagship projects of EU
In October 2013 EU launched its first two Flagship projects ever, Graphene and Human Brain Project (HBP). These FET Flagships are ambitious large-scale, sciencedriven, research initiatives that aim to achieve a visionary goal. Both of the flagships
are at their ramp-up phase and they should reach their steady phase in 2016. OVLL
participates in both of the flagships.
The Graphene Flagship aims at taking graphene
from the academic laboratories into European
society in the timespan of ten years, thus generating economic growth, new jobs and new opportunities for Europeans as both investors
and employees. The project is built around 11 specific science and technology areas
of research. The Finnish partners in the Graphene Flagship project are Aalto University, VTT Technical Research Centre of Finland and Nokia Finland. The research
groups run by Aalto University professors Pertti Hakonen (OVLL) and Harri Lipsanen
(Department of Micro and Nanosciences, School of Electrical Engineering) are responsible for sensor development and production of high frequency transistors.
The Human Brain Project aims at understanding the human
brain by building brain models to gain profound insights into
what makes us human, to develop new treatments for brain
diseases and to design revolutionary new computing technologies. The project is built around the research areas of future
neuroscience, future medicine and future ICT. Aalto University is HBP’s only Finnish partner, with professors Riitta Hari (OVLL) and Lauri
Parkkonen (Department of Biomedical Engineering and Computational Science,
BECS) taking care of the “Social brain” task of the project.
Other European projects
The collaboration with European partners was active and fruitful. In addition to the
Flagship projects, following projects were running in 2014:
Brain2Brain – Towards two-person neuroscience – is a research effort advancing from studies of single persons towards two-person neuroscience in multidisciplinary and unconventional approach. The project aims to demonstrate that the complex social shaping of the human
brain can be adequately tackled only by taking this important leap. The
results can lead to better understanding of human human interactions and also social
disorders, such as autism and schizophrenia. The advances in two-person neuroscience show promisevof a breakthrough in understanding the dynamic social shaping of
human brain and mind.
The project is an individual European Research Council (ERC) advanced grant allocated to Academician, Academy Professor Riitta Hari.
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InK – Implementing the new kelvin – is a project addressing
fundamental thermometry issues, which are a significant advance on the current state of the art. It is anticipated that the
new knowledge generated by the project will have a direct influence upon the mise en pratique for the definition of the kelvin (MeP -K). The project is expected to improve primary thermometry on a broad front. OVLL participates
with individual researcher excellence grant (REG) funded by the European Metrology
Research Programme of the European Association of National Metrology Institutes
(EURAMET).
QuAmpere – Quantum ampere: Realisation of the new SI
ampere – aims at further developing the best existing concepts
of SET pumps (single-electron transport devices needed to
control the number of electrons flowing in a unit time interval)
and to combine them with single-electron detectors to create highly accurate quantum
current sources, to be used as current standards in the future. Furthermore, the necessary associated instrumentation is developed. The key objective of the project is the
implementation of capabilities and methodologies for the realisation and dissemination
of the new SI base unit definition for the ampere. OVLL participates with individual
researcher excellence grant (REG) funded by the European Metrology Research Programme of the European Association of National Metrology Institutes (EURAMET).
HEATRRRONICS – Mesoscopic heattronics: thermal and
nonequilibrium effects and fluctuations in nanoelectronics – is a
research effort where the emergence of the subsystem temperatures in
different types of small electronic systems, and the physical phenomena associated with those temperatures is studied. The aim is to understand the fundamental properties of electronic systems, directly relevant for the development of thermal sensors and electron refrigerators. The results benefits also the
research of solid-state realizations of quantum computing and the race towards quantum limited mass and force detection.
The project is an individual European Research Council (ERC) grant allocated to Docent of OVLL Tero Heikkilä, currently working as a Professor at the University of
Jyväskylä.
INFERNOS – Information, fluctuations, and energy control in
small systems – is a European project where the primary goal is to
study both experimentally and theoretically the statistics of fluctuations and the role of information in thermodynamics of nanoscale
systems. The first milestone will be the experimental realization of
the so-called nanoscale Maxwell’s Demon*.
Infernos is coordinated by OVLL and it is funded by the European Union FP7 programme as a future and emerging technologies (FET) -project.
______________
* Maxwell’s Demon is an imaginary creature that the mathematician James Clerk Maxwell created in
1897. The creature could turn heat into work without causing any other change, which violates the second law of thermodynamics.
Annual Report 2014
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iQUOEMS – Interfacing Quantum Optical, Electrical, and Mechanical Systems –
is a European project aiming at the efficient realization of quantum interfaces for highfidelity conversion and coherent manipulation of quantum states of phonons and of
photons at vastly distinct wavelengths. The project results will enable new regimes for
radio- and microwave electro-magnetic field detection, allowing quantum-limited amplification and readout of microwave and radiofrequency radiation. At the same time
solid-state quantum devices which are now mainly manipulated by radiofrequencies
and/or microwaves will become efficiently coupled to and controlled by optical fields.
OVLL participates as one of the partners to this project funded by the European Union
FP7 programme as an ICT research project.
NEMSQED – Electromechanical quantum coherent systems – is a
research effort where superconducting and nanomechanical systems
ares studied near the quantum limit. The aim is to forge a hybrid macroscopic quantum system of superconducting qubits, electrical resonators and nanomechanical resonators, with highly beneficial potential
applications in quantum information processing and quantum communication.
The project is an individual European Research Council (ERC) grant allocated to Dr.
Mika Sillanpää, currently working as a Professor at the Department of Applied Physics
at Aalto University.
SOCIAL BRAIN – Brain mechanisms behind human social interaction – is a research effort where an unprecedented in-depth look is
taken into the functioning of the human brain. The aim is to find out
how the brain transfers information from person to person, and how the
brain stores information so that people are able to understand each other.
The project is an individual European Research Council (ERC) grant allocated to Docent, Academy Fellow Lauri Nummenmaa (BECS), shared with OVLL.
Q-NET – Quantum Nano-Electronics Training – is a European network of experts providing state-of-the-art training for
young researchers in the general field of experimental, applied
and theoretical Quantum Nano-Electronics. It aims at improving the conceptual understanding of quantum electron transport at the nanoscale, needed for enabling the emergence of “Beyond C-MOS“ nano-electronics devices, providing young researchers with excellent prospects for a career either in the industry or in
academia. OVLL participates as one of the partners to this project funded by the European Union FP7 programme as a Marie-Curie Initial Training Network for young
researchers.
Annual Report 2014
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SEMINARS AND WORKSHOPS
Kopnin symposium
24 January, 2014
In January 2014, a symposium was organized to commemorate professor Nikolai Kopnin who passed away suddenly and unexpectedly
at the end of 2013. He was a renowned theoretical physicist whose
research on superconductivity earned him a number of international
distinctions. At the symposium his recent coworkers described their
joint research with Nikolai Kopnin. In addition two of his children,
research scientists themselves, explained how their father inspired their own work. The
symposium gathered about 40 attendees at Otaniemi, Espoo.
Voiko aivotutkija lukea mieltäsi?
11 March, 2014
In March 2014, during the global Brain Awareness Week, aivoAALTO-project organized a public event called Can brain researcher read your mind? (Voiko aivotutkija
lukea mieltäsi?) The event consisted of several speeches and a panel by brain research
specialists. The event gathered wide audience in Helsinki.
Workshop on flat bands and room-temperature superconductivity
30 - 31 May, 2014
In May 2014, a workshop on flat bands and room-temperature superconductivity was
organized by the Centre of Exellence in Low Temperature Quantum Phenomena and
Devices (LTQ) in Otaniemi, Espoo. The workshop brought together experimentalists
and theoreticians working with graphene, graphite, flat bands, topological materials
and high temperature superconductivity.
5th Graphene and 2D Materials Satellite Symposium (GSS14)
7 June, 2014
In June 2014, the 5th Graphene and 2D Materials Satellite Symposium (GSS14) was
organized parallel with three other satellite symposia of the NT14: The Fifteenth International Conference on the Science and Application of Nanotubes. Prof. Pertti Hakonen chaired the symposium with Prof. Jeanie Lau from UC Riverside, CA (USA)
and Dr. Katsunori Wakabayashi from National Institute for Materials Science (Japan).
The symposium took place in Los Angeles, CA and it covered the latest progress in the
Graphene research. The symposium gathered over hundred participants from around
world.
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Aivot ja mieli, käsitteet ja kieli
13 - 14 October, 2014
In October 2014, Aalto Brain Center and Neuroscience Center of the University of
Helsinki organized second time a Symposium of the Finnish Society for Natural Philosophy called Brain and mind, concepts and language (“Luonnonfilosofian seura:
Aivot ja mieli, käsitteet ja kieli”) at Helsinki. The symposium brought together multidiciplinary audience and experts to discuss and enlighten our understanding on human
brain and mind.
3rd BRAHE symposium
22 October, 2014
In October 2014, the BRAHE (Brain Research at Aalto University and University of
Helsinki) Executive Board and the Doctoral Program Brain & Mind, organized the 3rd
BRAHE symposium with the focus on the infrastructures available in both universities. The meeting gathered nearly 150 neuroscientists from Aalto University (AU) and
University of Helsinki (UH) to present and discuss their most recent research in the
field of neuroscience. The symposium was organized at Helsinki.
TMS-fMRI Workshop 2014
30 October, 2014
In October 2014, Aalto Brain Center and Aalto NeuroImaging organized a TMSfMRI Workshop on functionality and plasticity of the brain. The orientation of the
workshop was to discuss challenges related to TMS-fMRI and to learn about studies
that have successfully applied these methods, while promoting TMS research at Aalto
University. The workshop gathered 45 attendees at Otaniemi, Espoo.
Aivokummien teemailtapäivä
31 October, 2014
In October 2014, researchers of the BRU organized a public event for people listed as
volunteer participants for brain imaging experiments. The event consisted of several
speeches on current scientific developments in the BRU and a tour of the MEG core.
The event had ~30 participants.
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GROUP VISITS
Aalto assistants, 20 visitors (22.5.)
Aalto communications team, 20 visitors (2.10.)
Aalto first year physics students, 10 visitors (9.12.)
AYY student union board and TOKYO Association board, 15 visitors (14.10.)
Helsinki capital region high school students, 20 visitors (6.11.)
Helsinki Summer School: Physics of Functional Materials -course, 14 visitors
(15.8.)
Hokkaido University students, 9 visitors (6.3.)
Kruunuhaka secondary school students, 17 visitors (15.5.)
Köln high school students, 20 visitors (15.1.)
MAOL Helsinki club, 15 visitors (3.12.)
Micronova staff members, 10 visitors (18.11.)
Millennium Youth Camp, 80 visitors (6.6.)
Ministry of Education and Science of the Russian Federation, 5 visitors (5.12.)
Porin Suomalainen Yhteislyseo high school students, 15 visitors (2.12.)
Teknologföreningen/ final year high school students, 30 visitors (7.11.)
Utajärvi high school students, 15 visitors (12.11.)
World Cultural Council, 10 visitors (20.11.)
Annual Report 2014
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LOW TEMPERATURE PHYSICS RESEARCH
KVANTTI group
Sergey Danilin, Karthikeyan S. Kumar, Aapo Taavitsainen, Antti Vepsäläinen, Sorin
Paraoanu
Visitors: Shirong Bu (visiting prof.)
Collaborators: P. Hakonen, M. Huuppola, O. Ikkala, C. Johans, L. Koponen, J. Li,
M.A. Oksanen, R.H.A. Ras, E. Seppälä, M. Sillanpää, M.P. Silveri, E.V. Thuneberg, J.
Timonen, and J. Tuorila
The main focus of our research are superconducting quantum circuits, a rich experimental platform where several Hamiltonians can be realized. In 2014 we started experiments on STIRAP and on qubit-induced nonlinearity of a cavity. We also concluded
a few other experiments, on Stueckelberg interference and on Co nanoparticles, on
which we will report below.
STUECKELBERG INTERFERENCE UNDER PERIODIC LATCHING
MODULATION
We observed an interference effect similar to the well-known Landau-ZenerStueckelberg-Majorana interference, but this time with a modulation shaped as a
square pulse. In this situation it can be shown that the Landau-Zener (LZ) probability
formula is not applicable. The reason is that the LZ approximation requires that the
points of phase accumulation are outside the transition region, and this does not happen for fast enough pulses1. We also published two review papers2, 3.
Figure 1: Image of the sample (left) and qubit spectra with a schematic of the experiment. The flux coil
of the transmon is modulated with a square pulse.
1
Silveri, M.P., Kumar, K.S., Tuorila, J., Li, J., Vepsäläinen, A., Thuneberg, E.V., and Paraoanu, G.S.,
Stückelberg interference in a superconducting qubit under periodic latching modulation, New. J. Phys.
17, 043058 (2015).
2
Paraoanu, G. S., Recent Progress in Quantum Simulation Using Superconducting Circuits, J. Low.
Temp. Phys. 175, 633-654 (2014).
3
Lähteenmäki, P., Vesterinen, V., Hassel, J., Paraoanu, G. S., Seppä, H., and Hakonen, P., Advanced
concepts in Josephson junction reflection amplifiers, J. Low. Temp. Phys. 175, 868-876 (2014).
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CO NANOCOMPOSITES AT MICROWAVE FREQUENCIES
Despite a lot of work in the field of nanocomposites, there is still no good understanding of how materials containing magnetic insertions behave in a microwave field. Our
measurements of the complex magnetic permeability of a nanocomposite made of Co
nanoparticles embedded in a PS matrix4 show that Kittel’s theory of ferromagnetic
resonance needs to be modified due to interparticle interactions.
Figure 2: The left picture in the TEM image of a single Co nanoparticle and (insets) a smallermagnification showing how they assemble. The right picture represents the measured imaginary part of
the complex permeability at microwave frequency (theory simulation in the inset).
4
Chalapat K., Timonen J., Huuppola M., Koponen L., Johans C., Ras R.H.A., Ikkala O., Oksanen M.A.,
Seppälä E., and Paraoanu G.S., Ferromagnetic resonance in epsilon-Co magnetic composites, Nanotechnology 25, 485707 (2014).
Annual Report 2014
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NANO group
Daniel Cox, Pertti Hakonen, Pasi Häkkinen, Olli Ihalainen, Jukka-Pekka Kaikkonen,
Manohar Kumar, Antti Laitinen, Pasi Lähteenmäki, Teemu Nieminen, Mika Oksanen,
Antti Puska, Jayanta Sarkar, Xuefeng Song, Zhenbing Tan and Matti Tomi
Visitors: K. Arutyunov, C. Flindt, A. Isacsson, G. Lesovik, T. Matsuura, K. Nagaev,
H. Nobukane, B. Placais, A. Semenov, E. Sonin, S. Tanda, and A. Zaikin
Collaborators: M.F. Craciun, D. Golubev, J. Hassel, T. Heikkilä, S. Paraoanu, S.
Russo, M. Sillanpää, E. Sonin, E. Thuneberg, J. Tuoriniemi, and P. Virtanen
The research work of the NANO group covers four areas: 1) Mesoscopic quantum
amplifiers and qubits, 2) Current fluctuations and fast dynamics in quantum circuits, 3)
Quantum transport in carbon nanotubes and graphene, and 4) Nanoelectromechanical
systems. In all of these categories, our measurements are centered at microwave frequencies, involving reflection measurements for qubits and qubit-like objects, transmission measurements for AC-conductance, and two-channel noise recording for cross
correlation studies.
1) QUANTUM AMPLIFIERS AND QUBITS
In qubit research, we have been collaborating with KVANTTI and NEMS groups. One
of the recent goals has been to utilize qubits to enhance coupling between NEMS resonators and microwave cavities in optomechanical settings.5 Studies of dynamical
Casimir effect have been continued in collaboration with the KVANTTI group. Using
double pumping on microwave cavities, we have investigated phenomena related to
vacuum-induced coherence between multiple frequencies.
DYNAMICAL CASIMIR EFFECT
We continued our studies of the dynamical Casimir effect with a Josephson metamaterial acting as an analog of a cavity with a moving mirror at the end.6 In these experiments, the material was pumped by high-frequency external magnetic field, which
leads to a non-adiabatic change of the material properties and modulation in the phase
of a reflected microwave signal. We searched for correlations between Casimir photons at the opposite ends of the cavity but, unfortunately, large dissipation along the
chain diminished correlations to an irrelevant level. In the course of this work, we
have also kept an eye on quantum amplifier applications of these devices.7
To avoid large dissipation, we employed a simpler design in the latest work, namely a
cavity with a lumped element SQUID mirror. We applied two pump signals at frequencies separated by distance, which was on the order of the bandwidth of the cavity.
Quantum fluctuations trigger two-photon decay in both pumps. The resulting photons
are correlated even if they originate from different pumps, due to the fact that they
5
Pirkkalainen, J.-M., Cho, S.U., Massel, F., Tuorila, J., Heikkilä, T.T., Hakonen, P.J., and Sillanpää,
M.A., Cavity optomechanics mediated by a quantum two-level system, Nat. Comm. 6, 6981 (2015).
6
Lähteenmäki, P., Paraoanu, G.S., Hassel, J., and Hakonen, P.J., Dynamical Casimir effect in a Josephson metamaterial, Proc. Nat. Acad. Sci. 110, 4234 (2013).
7
Lähteenmäki, P., Vesterinen, V., Hassel, J., Paraoanu, G.S., Seppä, H., and Hakonen, P., Advanced
concepts in Josephson junction reflection amplifiers, J. Low Temp. Phys. 175, 868-876 (2014).
Annual Report 2014
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were 'born into existence' by the same quantum fluctuation. This results in a tripartite
state with squeezing correlations between the neighboring frequencies and beamsplitter correlations between the extremal ones. This also results in the quenching of
the amplified vacuum fluctuations in the orthogonal superposition of the extremal
modes, which can be regarded as a parametric “dark” state. These are phase-sensitive
effects and can be controlled by the relative phase of the pumps.
Figure 3: Noise power observed in the two-photon decay under two external pumps marked by
solid lines (b). Note the reflection symmetry about the red lines. The correlations were measured
across the frequency three bandsbetween the dashed lines in (a).
SHOT NOISE IN QUANTUM PHASE SLIP WIRES
We have made noise investigations on quantum phase slip wires by looking for the
dual of the electronic shot noise, i.e. the shot noise of flux quanta in superconducting
nanowires. In analogy with the Fano-factor Fe describing the regular electronic shot
noise Fe2eI = Fe2e2f, we may define a flux jump Fano-factor describing the voltage
noise in a Josephson junction: Fϕ f, ϕ is the flux quantum and f is the frequency of
flux jumps. In other words, F here indicates the degree of bunching of the flux jumps
in the sample.
2
0
0
We measured shot noise in titanium nanowires prepared by the group of K. Arutyunov.
Even though the noise was small, we were able to distinguish phase slip noise from a
single nanowire. The noise was mapped as a function of bias and temperature, and
clear signatures of phase slip bunching were observed. However, quantum effects are
difficult to separate from thermal effects, because biasing leads quickly to heating of
the wire. Clearly, better models including Joule heating are needed for definite
conculsions.
At large bias, these wires enter the shot noise regime governed by electron-phonon
coupling. Our experiments (see Figure 4) yield for the electron-phonon coupling
temperature dependence proportional to T4 instead of the usual T5-dependence. This T4
dependence is quite seldom observed in mesoscopic systems but it is expected for
certain kind of disorder at low temperatures.
Annual Report 2014
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Figure 4: Shot noise vs. current in titanium a nanowire. Blue line indicates T4 dependence.
BLOCH OSCILLATING TRANSISTOR
The Bloch-oscillating transistor (BOT) is an amplifier that utilizes semiclassical dynamics of states in energy bands under traveling quasimomentum. In a BOT, a single
quasiparticle tunneling across a base tunnel junction switches the state of a superconducting tunnel junction to a lower Bloch band, triggering a series of resonant Cooperpair tunneling events through an emitter Josephson junction (Bloch oscillations). During 2014, we completed our experimental and theoretical investigation on an alternative
realization of this device, based only on superconducting tunnel junctions.8 We discovered new amplification schemes, where the periodic motion of the quasimomentum is
used to control charge transport between the electrodes. In the operation, remarkably,
the resonant Cooper-pair transport across the base Josephson junction occurs repeatedly
in two opposite directions.
A continuous current flow to the superconducting island is established by voltage biasing a high-resistance thin-film resistor in the immediate vicinity of the transistor island.
This drives the quasimomentum of the system, corresponding to the charge flow between the island and the collector. Connection to the emitter and the base is realized
through superconducting tunnel junctions. When biased below the superconducting
gap, we find that the periodic motion of the quasimomentum controls Cooper-pair
transport across the emitter and the base junctions. Near two operation points the system can be made to switch between largely differing transport regimes by a small
change in the base current. At high tunnel couplings the transport is found to bifurcate,
so that the behavior becomes hysteretic at the two operation points.
2) CURRENT FLUCTUATIONS AND FAST DYNAMICS IN QUANTUM
CIRCUITS
SHOT NOISE CORRELATIONS IN GRAPHENE BOX
We have measured shot noise cross-correlations around 750 MHz in a graphene box
with corner electrodes (see Figure 5a). Shot noise was measured from terminals 1 and 4
while the two other terminals were used for DC bias. The determination of the Han8
Leppäkangas, J., Puska, A., Äkäslompolo, L., Thuneberg, E., and Hakonen, P.J., Fully superconducting Bloch-oscillating transistor: Amplification and bifurcation based on Bloch oscillations and counterflowing Cooper pairs, [arXiv:1412.7431].
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bury-Brown & Twiss (HBT) exchange correction factor involves correlation measurements from three different bias configurations, A, B and C. The measured HBT exchange correction factor ∆𝑆 = 𝑆! − 𝑆! + 𝑆! is shown in Figure 5b as a function of gate
and bias voltages. At low gate voltage the scaled exchange correction factor ∆𝑆/(𝑆! +
𝑆! ) !! →! ≈ -0.2, which is close to the theoretical value -0.188 for a side-contacted
box geometry9. The theoretical result was confirmed with numerical simulations using
semiclassical equations in order to take account for the difference in the electrode
placement between our measurements and the theoretical result of Blanter and Büttiker. The measured exchange correction factor approaches zero as the gate voltage is
increased towards the Dirac point (see Figure 5b).
(a)
(b)
Figure 5: (a) Scanning electron microscope (SEM) image of the sample with the four electrodes
numbered, length of graphene edge 360 nm; (b) Measured ∆𝑺 (arb. units) as a function of gate
and bias voltages.
COOPER PAIR SPLITTING BY MEANS OF GRAPHENE QUANTUM DOTS
Quantum entanglement is at the heart of Einstein–Podolsky–Rosen (EPR) paradox,
which is fundamental for quantum information. Quantum entanglement has been successfully realized in optics, where the experiment benefit from the easy generation of
entangled photons. In solid state, however, the progress has been modest. One natural
source for quantum entanglement in solid state is split Cooper pairs. A Cooper pair,
split out from a superconductor into two different terminals, will form a non-local entangled spin pair. We report an experiment on a superconductor-graphene double
quantum dot (QD) system, in which we observe Cooper pair splitting (CPS) up to a
CPS efficiency of ~ 10%.10 Comparing to the previous Cooper pair splitters, we were
able to independently tune the bias and the energy levels of the two graphene QDs.
Benefit from that, for the first time, the energy levels of the two QDs were tuned to be
asymmetric or symmetric with respect to Fermi level in the superconductor. And we
observed CPS or elastic co-tunneling favored as theories predicted (see Fig. 5. in
Ref.10.). The realization of CPS in graphene makes it feasible for graphene to be used
for quantum information processing.
illustrates the behavior in our CPS device using unequal biasing voltage on the
two splitter-arms 1 and 2; clearly, the splitting efficiency increases with unequal bias.
Figure 6
9
Blanter Ya.M., and Büttiker, M., Physical Review B 56, 2127 (1997).
10
Tan, Z.B., Cox, D., Nieminen, T., Lähteenmäki, P., Golubev, D., Lesovik, G.B., and Hakonen, P.J.,
Cooper Pair Splitting by means of Graphene Quantum Dots, Phys. Rev. Lett. 114, 096602 (2015).
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The increase of non-local Δg2 with bias Vac1 can be understood according to the schematic picture in Figure 6d. With higher Vac1, there will be a wider bias window for CPS
as shown by the dash-dotted arrow in Figure 6d, which leads to an increase in Δg2. Although Vac1> Vac2, elastic cotunneling (EC) causes an opposite current on QD2, making
Δg2 to decrease. The observed overall increase in Δg2 indicates that CPS is stronger
than EC under this circumstance. It is to be noted that we only sketch the positive bias
part in Figure 6d. For the negative bias part, the result will be equivalent.
Figure 6: (a) False color SEM image of our CPS device for the measurement configuration with
unequal bias voltages. The white scale bar is 500 nm. (b) Upper frame: Resonance oscillations
of g1 as a function of Vsg1 under bias Vac1 = 20 µV, 100 µV and 200 µV, respectively. Lower
frame: Nonlocal conductance Δg2 as a function of Vsg1 under Vac1 = 20 µV, 50 µV, 100 µV, 150
µV and 200 µV, respectively. Vac2 was kept as constant at 20 µV, Vbg = 5 V, and Vsg2 = 0 V. (c)
Upper frame: Maximum nonlocal conductance Δg2vs. Vac1 measured at the resonance conductance peaks at Vsg1 = -0.18 V, 0.11 V and 0.541 V, respectively. Lower frame: Widths at half maximum of g1 (rectangle marks) and Δg2 (triangle marks) vs. Vac1measured at the same resonance
peaks at Vsg1 = -0.18 V, 0.11 V and 0.541 V, respectively. (d) Schematic illustration of CPS and
EC under unequal bias configuration on the two QDs.
3) QUANTUM TRANSPORT IN CARBON NANOTUBES AND
GRAPHENE
The NANO-group is involved in the European Graphene Flagship project, which
forms the backbone of the graphene related work in the group. Owing to substantial
synergy between graphene and carbon nanotube CVD production, work on highquality carbon nanotubes fits well together with graphene. Many of the theoretical
concepts are shared, which allows plenty of synergy between these two research fields.
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TRANSPORT ON SUSPENDED ULTRA-PURE SINGLE-WALLED CARBON
NANOTUBES
Quantum dot (QD) devices made out of suspended single-walled carbon nanotubes
(SWNT) have been investigated at cryogenic temperatures. The SWNTs were grown
as a final step of the sample fabrication on top of superconducting Nb/Pt electrodes.
The critical temperature of the electrodes is reduced from 9 K to approximately 4 K
during the high temperature CVD growth. The dI/dV vs. VG plot in Figure 7 demonstrates typical behavior found in SWNT quantum dots. The conductance peaks are arranged in groups of four due to the spin and orbital degeneracy. Inside a voltage window of 1.44 V around the zero gate voltage, the Fermi levels of the source and drain
electrodes reside within the energy gap of the SWNT, and no current flows through the
device. The behavior on negative and positive VG is slightly different. In the hole conductance region, VG < 0 V, the contacts are less transparent than on the electron conductance region, VG > 0. Sharp Coulomb peaks arise in both regions. The IV-curve in
Figure 7 shows that the device supports small but measurable supercurrent at the highest
conductance region on the electron side.
Figure 7: (left) The dI/dV vs. VG, measured at 50 mK, sws Coulomb peaks on the whole gate range. The
electron conduction side is more strongly coupled to the electrodes which is seen from the higher conductance of the positive gate voltage side. (right) On regions with highest conductance we measure
small gate controllable supercurrent with a maximum switching current of 40 pA.
PN-INTERFACES IN GATED SUSPENDED GRAPHENE
The nature and density of charge carriers in pristine graphene can be controlled by
electrostatic gating in graphene FETs. The suspended part of a high quality suspended
graphene device is close to this ideal situation. However, in real devices the graphene
flake needs to be contacted with metallic leads with work function that differs from
graphene’s own work function. This inevitably leads to doping of graphene under the
leads. Thus, when the free gate-controlled part of the graphene is tuned properly (opposite charge doping compared to the leads) pn-interfaces are formed at the edge of
the suspended part near the contacts.
We have developed a model to analyze the transport properties of the pn-junctions
formed near the contacts.11 The model based on the Dirac equation leads to Klein tunneling through the pn-barriers, which produces distinctive features that can be seen in
our low frequency conductance measurements and high frequency shot noise results.
Additionally, the measurement data was used to estimate the doping of graphene by
11
Laitinen, A., Paraoanu, S., Oksanen, M., Craciun, M.F., Russo, S., Sonin, E., and Hakonen, P., Klein
tunneling, contact doping, and pn-interfaces in gated suspended graphene, [arXiv:1502.04330].
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the Cr/Au contacts, ~-18 meV, and the barrier thickness d < 20 nm. During this work,
we also realized that the work function of the gate material plays a role (even under
the suspended part), and if this work function is different from graphene, the difference in work functions will lead to an initial doping of the graphene - back gate capacitor.
(b)
(a)
Figure 8: (a) Schematic of the doping model at one of the contacts displaying the metal on the left,
metal contacted graphene in the middle, and gate-controlled graphene on the right. (b) The measured conductivity near the Dirac point (blue circles) and the curve produced by the theory.
ELECTRON-PHONON COUPLING IN SUSPENDED BILAYER GRAPHENE
Using electrical transport experiments and shot noise thermometry, we investigated
electron-phonon heat transfer rate in a suspended bilayer graphene.12 Contrary to suspended monolayer graphene with heat flow via three-body supercollision scattering
involving dynamic ripples13, we find that regular electron - optical phonon scattering
in bilayer graphene provides the dominant scattering process at electron energies !
0.15 eV. We determine the strength of these intrinsic heat flow processes of bilayer
graphene at electronic temperatures of 300 -­‐ 1000 K, induced by bias voltages comparable to optical phonon energies. The strength of the scattering follows theoretical expectations with a specific thermal activation behavior, and indicates the presence of
intervalley electron scattering by zone edge and zone center optical phonons. This
electron-phonon coupling is found to be independent of the chemical potential at |µ| <
12 meV, which is in accordance with the theory for optical phonon scattering.
12
Laitinen, A., Kumar, M., Oksanen, M., Plaçais, B., Virtanen, P., and Hakonen, P., Electronoptical phonon coupling in suspended bilayer graphene, Phys. Rev. B 91, 121414(R) (2015).
13
Laitinen, A., Oksanen, M., Fay, A., Cox, D., Tomi, M., Virtanen, P. and Hakonen, P., Electronphonon coupling in suspended graphene: supercollisions by ripples, Nano Lett. 14, 3009 (2014).
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Figure 9: Heat flow to the electron system normalized with T3. The red circles are data, the solid blue line denotes the theoretical optical phonon contribution including the zone edge and center contributions, and the black dashed
line corresponds to sum of the blue curve and the thermal conductance due to
electronic diffusion according to the Wiedemann-Franz law.
SUPERCONDUCTOR–GRAPHENE–SUPERCONDUCTOR JUNCTIONS
We have measured electron transport and shot noise in superconductor–graphene–
superconductor (SGS) junctions at temperatures below 100 mK. Monolayer graphene
sheets were contacted by Al leads with a thin 10 nm layer of Ti between graphene and
Al to achieve contacts with high transparency. Graphene strips were kept short (200300 nm) and wide so that contribution from the sheet edges would be negligible.
Below the superconducting gap we observe clear signs of multiple Andreev reflections
(MAR) in the conductance, similar to superconductor–normal-metal–superconductor
(SNS) junctions. The lack of sharpness in the MAR features near 2Δ/n (n=1, 2, 3…)
indicates that although our samples are very short, they are still longer than the superconducting coherence length ξ. We also notice a clear reduction of gap voltage, while
tuning the charge carrier concentration in graphene through a back gate. At non-zero
gate voltages the resistance of graphene decreases, which causes more Joule heating at
a given bias voltage (𝑃 = 𝑉 ! /𝑅), leading to a higher temperature and a reduced gap
voltage. As the device is predominantly thermalized through the superconducting leads
(𝑃 ∝ 𝑇 ! − 𝑇!! ), we can determine the effective electronic temperature of the sample
by using the well-known BCS theory relation between gap voltage and temperature.
In the incoherent regime, i.e. when the length of the graphene section is longer than the
superconducting coherence length (𝐿 > 𝜉) and biasing is larger than Thouless energy
(𝑒𝑉 > 𝐸!" ~10 µeV), current noise is governed by the effective electronic temperature.
In our SGS samples we find that the measured noise is in good agreement with the incoherent model. Altogether, our results underline the importance of thermal effects in
studies of diffusive graphene Josephson junctions at finite bias.
1/f NOISE IN SUSPENDED BILAYER GRAPHENE
Our investigations on 1/f noise in suspended bilayer graphene sheets displayed ultralow noise in all our pristine devices near the Dirac point. The low frequency noise level was insensitive to intrinsic carrier density but sensitive to temperature and contact
area. We studied the 1/f noise w.r.t. temperature and extrinsic doping. High extrinsic
doping and temperature evoke carrier density fluctuations, whereas in pristine samples
the 1/f noise is dominated by noise at the contacts. Due to their low intrinsic 1/f noise
Annual Report 2014
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level, large surface area and sensitivity to external perturbations, suspended bilayer
graphene devices can provide an exciting platform for gas sensing applications.
Typically, 1/f noise is produced due to charge trapping and mobility fluctuations when
electrical current flows. However, in our high-quality suspended graphene bilayers, the
noise from contacts appears to dominate. This is concluded from gate sweeps where
the 1/f noise is nearly independent of the charge carrier density (See Figure 10). Since
conductance grows linearly with charge density n, the conductance fluctuations have
to scale as n as well. The simplest model to fulfill this requirement is that the fluctuation is in the transmission eigenvalues, the number of which grows linearly with
charge density. Thus contact noise overshadows the contribution coming from the graphene sheet itself that has dominated the noise for instance in monolayer devices. Consequently, we obtained the lowest 1/f noise level compared with any other novel
nanocarbon material, on or off substrate (encompassing mono- and bilayer graphene
and carbon nanotubes).
Figure 10: Resistance and low frequency
noise characteristics for a bilayer sample (L
= 1.2 mm and W = 3.1 mm) w.r.t. charge
carrier density. The low frequency noise
was measured at Ib = 53 mA. The dashed
line yields fSI/Ib2 = 7:5 × 10−9.
4) NANOELECTROMECHANICAL SYSTEMS
Together with the NEMS group, we have investigated nanoelectromechanical systems
made out of aluminum and graphene, and lately even single walled carbon nanotubes.
The accessibility of quantum phenomena in (nonlinear) optomechanical settings at microwaves has improved lately along with the graphene technology. Due to its extreme
lightness and large Young’s modulus, the characteristic resonant frequencies will be so
high that 0.1 – 1 GHz nanoelectromechanical resonators can be manufactured. Secondly, the quantum zero-point vibrations in graphene (or SWCNTs) are orders of magnitude larger in amplitude than in metallic resonators, and hence easier to detect and manipulate.
CARBON NANOTUBE RESONATORS AS CHARGE DETECTORS
Strong coupling between the mechanical degree of freedom and charge dynamics in
single-walled carbon nanotube mechanical resonator causes appreciable changes in the
electrical properties of the device under resonant conditions.14 Mechanical-oscillationinduced change in the conductance G of the SWNT, together with the dc-gate voltage
VG0 dependence of the resonance frequency, can increase the transconductance of the
14
Häkkinen, P., Isacsson, A., Savin, A., Sulkko, J., and Hakonen, P., Charge sensitivity enhancement
via mechanical oscillation in suspended carbon nanotube devices, Submitted for publication.
Annual Report 2014
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device, see Figure 11. This enables effective reduction of the influence of noise sources
that do not couple directly to the gate electrode.
Figure 11: Conductance of the
SWNT SET measured against
gate voltage around one charge
degeneracy point. Fixed frequency
ac-excitation is applied to the gate
electrode. Sharp features appear
on both sides of the Coulomb
peak, when gate voltage dependent resonance frequency is in resonance with the ac-drive. The
inset reveals that the slope
𝝏𝑮/𝝏𝑽𝐆 can be significantly increased by the mechanical motion.
Increased transonductance allows reaching record charge sensitivity of single-electron
transistors. The best result was reached by biasing the resonator to a point where the
single-electron-tunneling induced Duffing constant is canceled out, and the
mechanical properties are determined mainly by the 5th order conservative
nonlinearity. This not only gives the optimal sensitivity of 0.97 𝑒/ Hz at ~1.3 kHz
but also results in an interesting mechanical response.8
Mechanical response curves measured at the optimal charge detection point are
displayed in Figure 12. When the Duffing constant is minimized, the resonator is found
to have response of a driven nonlinear resonator 𝑥 + 𝛾𝑥 + 𝛽𝑥 ! 𝑥 + 𝜔!! 𝑥 + 𝛼𝑥 ! +
𝜂𝑥 ! = 𝑓!" 𝑐𝑜𝑠𝜔! 𝑡. Here γ is linear damping constant, β nonlinear damping constant,
ω0 angular resonance frequency, α the Duffing constant, η coefficient of the 5th order
conservative nonlinearity, and ωD angular frequency of the applied force which has
amplitude fac.
Figure 12. (a)-(d) Source drain dc-current ISD as function of ac-frequency fD measured with
different ac-excitation levels. Sample is biased to the point where the electron-tunneling induced
Duffing constant is nearly canceled out. Black circles are measured data while lines are
theoretical fits. (a) At low drive power resonance displays softening nonlinear behavior due to
small residual Duffing constant. (b)-(c) The resonance peak start to bend to higher frequencies at
intermediate drive powers. This is caused by the 5th order stiffening nonlinearity. (d) At high
drive powers, mechanically induced gate charge oscillations traverse the Coulomb blocade peak
resulting in current saturation and reduction, eventhough the oscillation amplitude increases.
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GRAPHENE OPTOMECHANICS AT MICROWAVE FREQUENCIES
Graphene can be considered as an ultimate material for studying the quantum mechanical behavior of motion of micromechanical resonators, due to its light weight and
high stiffness. We have studied the lowest flexural mode of a bilayer graphene resonator at ωm/2π = 24 MHz, coupled to a superconducting microwave cavity. We observed
thermal motion down to 70 mK, and carried out backaction sideband cooling to dampen the mode temperature further down to 60 mK. 15
The increase of the effective damping experienced by the graphene resonator due to
red detuned driving of the cavity, is counteracted by Joule heating of graphene by circulating microwave currents (Figure 13a). A straightforward way to improve sideband
cooling efficiency at lower cavity occupancy is to increase the coupling between graphene resonator and the microwave cavity. To this end we have fabricated graphene
resonators with vacuum gaps down to 30 nm (Figure 13b). We estimate that by increasing the coupling g/2π = 600 Hz from the 35 Hz in the current experiment, would allow
cooling to the ground state.
Figure 13: (a) Demonstration of sideband cooling using graphene mechanical resonators. Due to
Joule heating, the phonon number in the graphene resonator decreases only from about 65 to 50.
(b) A prototype multilayer graphene resonator with 30 nm gap to gate electrode.
Recently, we have designed and fabricated new superconducting RF circuits for the
readout of graphene mechanical resonators in optomechanical settings at microwave
frequencies. The use of Nb circuits provides us high Q-factor, good power stability,
and a wide temperature range to work with. Investigations for the applicability of
highly inductive superconducting materials based on thin TiN films were started.
15
Song, X., Oksanen, M., Li, J., Hakonen, P. J., and Sillanpää, M. A., Graphene optomechanics realized at microwave frequencies, Phys. Rev. Lett. 113, 027404 (2014).
Annual Report 2014
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NEMS group
Mika Sillanpää, Matthias Brandt, Erno Damskägg, Caspar Ockeloen, Juha-Matti
Pirkkalainen, Jorge Santos, Jaakko Sulkko
The research work of the NEMS group is focused on studies of nanomechanical resonators near the quantum ground state of moving objects. We aim on observing quantum superposition states of motion by coupling vibrating beams to quantum electrical
circuits built upon superconducting junctions or resonators. We also investigate quantum phenomena in such superconducting junction qubits.
INTEGRATION
QUBITS 16
OF
MICROMECHANICS
WITH
SUPERCONDUCTING
Juha Pirkkalainen, Erno Damskägg, Matthias Brandt, and M. A. Sillanpää
In our earlier work17, we have coupled a superconducting qubit to a vibrating aluminum sheet using longitudinal coupling to the qubit. At the base temperature of cryostat, this required exciting the mechanical resonator occupation with an external drive
to attain high enough coupling between the two systems. We have anticipated that with
qubit lifetimes around one microsecond, single quantum of energy could be coherently
swapped between the systems.
Transmon qubits have turned out to be extremely robust with lifetimes well beyond
one microsecond. We have changed the fabrication process of our mechanical resonators and we are now able to create drum-like mechanical resonators with 20 times better quality factors and bigger capacitance modulations (Figure 14a). With the new mechanical drums we have been able to observe mechanical sidebands with deep transmon regime qubits (Figure 14b) where the mechanical coupling is transversal. For this,
we have developed a measurement setup to create longitudinal drive of the qubit. By
splitting the qubit excitation drive and cancelling the transversal component using a
phase delay between the two, we can obtain purely longitudinal qubit drive.
Figure 14: (a) Optical micrograph of the chip showing the interdigital-capacitor transmon qubit,
and the small drum-shape micromechanical resonator (top). (b) Two-tone spectroscopy of the
qubit 0-1 transition while driving the mechanical resonator at varying frequency around the resonance. The qubit spectral line (horizontal blue line at left and right) experiences a Stark shift at
the mechanical resonance, as well as develops mechanical sidebands.
16
Pirkkalainen J.-M. et al., unpublished.
17
Pirkkalainen, J.-M., Cho, S.U., Li, J., Paraoanu, G.S., Hakonen, P.J., and Sillanpää, M.A., Hybrid
circuit cavity quantum electrodynamics with a micro-mechanical resonator, Nature 494, 211-215
(2013).
Annual Report 2014
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NANOPOSITIONING OF NARROW VACUUM GAPS FOR SILICON NITRIDE
MEMBRANES
Matthias Brandt, Jaakko Sulkko, Juha Pirkkalainen, and M. A. Sillanpää
It would be highly beneficial to increase the intrinsically small radiation-pressure coupling between microwave cavities and mechanical resonators. The coupling is proportional to the inverse square of a narrow vacuum gap between the conducting resonator
and a back electrode. We achieve 50 nm gaps nowadays with drum and bridge resonators with microfabrication, however, a fully different approach is ongoing. We use a
cryogenic Attocube nanopositioning system, which is used to compress a top chip towards the vibrating membrane (Figure 15). This way, we estimate to achieve down to 1
nm gaps. This will allow radiation-pressure couplings up to 50 kHz and hence could
let us enter a single-photon strong-coupling regime. The work is done in collaboration
with Technion.
Figure 15: Cryogenic nanopositioning system. The picture shows a cross-section of a chip.
The needle on top is actuated at sub-Å precision. One goal is to narrow down the vacuum gap
between the vibrating bottom SiN membrane and the top electrode which is also made of SiN
membrane. The setup can also be used to tune the mode frequencies.
PIEZOELECTRIC OPTOMECHANICAL CRYSTALS
Caspar Ockeloen, and M. A. Sillanpää
Optomechanical crystals localize optical and mechanical modes into a small volume,
and hence maximize their coupling. If made out of piezoelectric material, such devices
could mediate the coupling between optical and microwave frequencies. The latter is
because the piezoelectricity allows for strong coupling to low-frequency electric fields.
We have started to investigate the possibility by making simulations of such a structure made out of Gallium Nitride, which is a single-crystal piezoelectric material and
presumably has low losses both optically and mechanically. We find that the dominant
optomechanical modes also couple to microwave fields (Figure 16), thus showing
promise for the integration.
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Figure 16: (left) Comsol simulation of the localized optical-mechanical mode at 4.7 GHz. The
colorcode shows the electric potential. (right) corresponding microwave S-parameters.
Annual Report 2014
– 35 –
PICO group
Massimo Borrelli, Timothe Faivré, Anna Feshchenko, Simone Gasparinetti, Dmitry
Golubev, Robab Najafi Jabdaraghi, Ivan Khaymovich, Jonne Koski, Elsa Mannila,
Hung Nguyen, Ville Maisi (MIKES), Matthias Meschke, Jukka Pekola, Joonas Peltonen, Ilmo Räisänen, Olli-Pentti Saira, Shilpi Singh, Mathieu Taupin, and Klaara
Viisanen.
Visitors and Collaborators: Joachim Ankerhold (University of Ulm, Germany),
Marco Arzeo (Chalmers University of Technology, Sweden), Geresdi Attila (Budabest
University of Technology and Economics, Hungary), Alessandro Braggio (SPINCNR, Italy), Andrew Cleland (University of California – Santa Barbara, USA),
Michele Campisi (Scuola Normale Superiore, Pisa, Italy), Bivas Dutta (Indian Institute
of Technology, Kalyanpur, India), Rosario Fazio (Scuola Normale Superiore, Pisa,
Italy), Yuri Galperin (University of Oslo, Norway), Attila Geresdi (Kavli Institute of
Nanoscience, Delft University of Technology, NEtherlands), William Halperin
(Northwestern University, Evanston, Illinois, USA), David Haviland (KTH Royal Institute of Technology, Sweden), Frank Hekking (CNRS Grenoble, France), Andrew
Higginbotham (Niels Bohr Institute, University of Copenhagen, Netherlands), Thomas
S. Jespersen (Niels Bohr Institute, University of Copenhagen, Netherlands), Peter
Kopnin (Alikhanov Institute for Theoretical and Experimental Physics, Russia), Helen
Kopnina (The Hague Univesity of Applied Science, Netherlands), Ferdinand
Kuemmeth (Niels Bohr Institute, University of Copenhagen, Netherlands), Chuan Li
(University of South Paris, France), Graham Machin (National Physical Laboratory,
UK), Charles Marcus, (University of Copenhagen, Netherlands), Alexander Mel’nikov
(Institute for physics of microstructures RAS, Russia), Shuji Nakamura (National Institute of Advanced Industrial Science and Technology, Japan), Karl Petersson (Niels
Bohr Institute, University of Copenhagen, Netherlands), Hugues Porthier (French Alternative Energies and Atomic Energy Commission, France), Maura Sassetti (SPINCNR, Italy), Yasuhiro Utsumi (Mie University, Japan), David van Zanten (Institute
Neel, France), and Maciej Zgirski (Institute of Physics, Poland).
The research work of the PICO group is focused on single electron tunneling, statistical and thermodynamic properties of classical and quantum nanostructures, electronic
refrigerators and thermometers, and superconducting quantum circuits. The main
achievement during 2014 was the realization of a Maxwell’s demon, analogous to famous Szilard engine, in a single electron box. Another set of experiments revealed
quasiparticle and Andreev processes in single-electron turnstiles down to single particle level. Activity in electronic refrigerators has also been continued and resulted in
further progress towards a cooler platform with enhanced power. The performance of a
superconducting quantum interference proximity transistor (SQUIPT) for detection of
tiny magnetic fields was improved significantly. We have continued our efforts to develop of the fast nanothermometer (in the first place for thermodynamics experiments),
and the standard Coulomb blockade thermometry toward low mK temperatures. We
have also studied thermometers operating at low bias and based on Andreev tunneling
as well as Josephson effect.
Annual Report 2014
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MAXWELL DEMON AND NON-EQUILIBRIUM FLUCTUATION RELATIONS
Jonne V. Koski, Ville F. Maisi, Jukka P. Pekola, Dmitri V. Averin, T. Sagawa, S.
Suomela, P. Solinas, J. Ankerhold, T. Ala-Nissila, Vera Gramich.
The field of non-equilibrium thermodynamics attracts a lot of attention in recent years.
Its rapid development has been triggered by the discovery of non-equilibrium fluctuation relations of statistical mechanics, e.g., Jarzynski18 and Crooks equalities19, which
relate the probabilities of positive and negative fluctuations of entropy of a mesoscopic
system. From the technological point view aluminum-copper single electron transistors
in the regime of strong Coulomb blockade, which we routinely fabricate in our lab,
provide an ideal test ground for non-equilibrium thermodynamics both in classical and
in quantum regimes. In the latter regime the coupling between a quantum system, e.g.
qubit, and the environment becomes very important.
One of the most important ideas of statistical mechanics is the relation between information and entropy, which is most clearly illustrated by the concept of Maxwell demon. A Maxwell demon is an object that measures the microscopic state of a system
and drives it to extract work or store energy with the aid of the measurement outcome.
We have realized an electronic Maxwell demon in a single electron box20, which is
conceptually very similar to Szilard engine21. We have shown that it approaches the
theoretical limit of kBTln2 for the amount of energy extracted from the thermal bath
per cycle.
18
Jarzynski, C., Nonequilibrium equality for free energy differences, Phys. Rev. Lett. 78, 2690 (1997).
19
Crooks, G. E., Entropy production fluctuation theorem and the nonequilibrium work relation for free
energy differences, Phys. Rev. E 60, 2721 (1999).
20
Koski, J.V., Maisi, V.F., Pekola, J.P., and Averin, D.M. Experimental realization of a Szilard engine
with a single electron, PNAS 111, 13786 (2014).
21
Szilard, L., Über die Entropieverminderung in einem thermodynamischen System bei Eingriffen intelligenter Wesen. Z. Phys 53, 840 (1929).
Annual Report 2014
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Figure 17: (A) The original proposal of “Szilard engine”: a box containing a single molecule is
split into two equal sections (Top Left). The section holding the molecule is allowed to expand up
to the full volume of the box (Top Right). Then the partition is introduced again and the process repeats. (B) Sketch of the energy diagrams allowing a similar cycle in the SEB. Work is extracted
when the particle is thermally excited to the higher energy state. (C) Experimental realization of the
SE as SEB. An excess electron is located on one of the two metallic islands, corresponding to the
first step on A and B. (D) The measurement and feedback parts of our MD operation. An SET electrometer on the bottom detects the electron, while the gate voltage Vg is applied to control the tunneling of the extra electron (to “move the wall”) trapping it capacitively. As Vg is slowly driven
back to the original setup in C, the net extracted work kBT ln 2 is produced by thermal activation as
indicated in the third step of B. (E) A time trace of the excess electron location, signaled by the
SET current Id. The bottom trace shows the applied gate-voltage signal that provides feedback.
Here ng = CgVg/e, with Cg being the coupling capacitance between the gate electrode and the gated box island.
We have further demonstrated for the first time22 that single electron box Maxwell
demon operates in accordance with Jarzynski equality modified to account for the information used in a feedback control23.
22
Koski, J.V., Maisi, V.F., Sagawa, T., and Pekola, J.P., Experimental Observation of the Role of Mutual Information in the Nonequilibrium Dynamics of a Maxwell Demon, Phys. Rev. Lett. 113, 030601
(2014).
23
Sagawa, T., and Ueda, M., Phys. Rev. Lett. 104, 090602 (2010).
Annual Report 2014
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Figure 18: (a) The single electron box (SEB). It is monitored by a single electron transistor (SET),
whose current Idet depends on n, the number of excess electrons on the right island of the SEB. The
SEB is controlled by gate voltage Vg. (b) Single trace histogram of detector signal for states n=0
(peaks to the left) and n=1 (peaks to the right) for different error probabilities e. (c) A full trace of the
feedback control. Idet shows the measured occupation in the SEB. (d) The measured work distribution.
(e) The distribution of work plus mutual information. (f) Test of Jarzynski equality for different probabilities of errors e. The equality does not hold for work W, but holds for the combination W/kBT + I.
We have theoretically investigated the dynamics of an open quantum system described
by Bloch-Redfield equations, focusing on the implications of fluctuation relations. The
exchange of heat between the system and environment plays an important role in this
context. We have studied in detail the so called two-measurement protocol, in which
the work extracted from a quantum system is defined simply as the difference of its
energies before and after an experiment. We have emphasized the importance of
commutation relation between system Hamiltonian and its derivative in this context24.
In another publication we have derived the distribution of heat exchanged between a
periodically driven two level system and thermal environment25. We have also studied
the heat exchange, which occurs between initially uncoupled quantum system and its
environment after they are brought in contact26. Finally, we have shown that strong
driving of a quantum system coupled to environment may strongly enhance Lamb shift
of its energy levels making it easier to detect27.
SINGLE ELECTRON TURNSTILE
Dmitri Averin, Christian Flindt, Dmitry Golubev, A. Heimes, Dania Kambly, Antti
Kemppinen, Sergey Lotkhov, Ville Maisi, Michael Marthaler, Juha Muhonen, Mikko
Möttönen, Yuriy Pashkin, Jukka Pekola, Olli-Pentti Saira, and Gerd Schön
The hybrid single electron turnstile28 consisting of a normal metal island with superconducting leads (SINIS) is one of the candidates for a metrological current standard.
24
Suomela, S., Solinas, P., Pekola, J.P., Ankerhold, J., and Ala-Nissila, T., Moments of work in the twopoint measurement protocol for a driven open quantum system, Phys. Rev. B 90, 094304 (2014).
25
Gasparinetti, S., Solinas, P., Braggio, A., and Sassetti, M., Heat-exchange statistics in driven open
quantum systems, New J. Phys. 16, 115001 (2014).
26
Ankerhold, J., and Pekola, J.P., Heat due to system-reservoir correlations in thermal equilibrium,
Phys. Rev. B 90, 075421 (2014).
27
Gramich, V., Gasparinetti, S., Solinas, P., and Ankerhold, J., Lamb-Shift Enhancement and Detection
in Strongly Driven Superconducting Circuits, Phys. Rev. Lett. 113, 027001 (2014).
28
Pekola, J.P., Vartiainen, J.J., Möttönen, M., Saira, O.-P., Meschke, M., and Averin, D.V., Hybrid single-electron transistor as a source of quantized electric current, Nature Phys. 4, 120 (2008).
Annual Report 2014
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Ideally, the turnstile can pump a single electron in each gate cycle resulting in an electric current proportional to the product of the electron charge and the frequency of
pumping, I=ef. Error processes limit the accuracy of these turnstiles and the focus of
our research is in understanding and eliminating such unwanted effects. Nonequilibrium quasiparticles in aluminium superconductor need to be controlled and
eliminated at low operation temperatures. In order to address this problem, we have
earlier fabricated and measured
NISIN turnstiles with a superconducting island in the middle.29 It has been shown in
that publication that the excitation and relaxation dynamics of non-equilibrium quasiparticles can be well described by standard model of electron-phonon interaction
within effective temperature approximation. We have further developed this theory by
going beyond this approximation and finding the full non-equilibrium distribution
function of quasiparticles in the island by solving the corresponding kinetic equation30.
We also include parity effect in the superconducting grain. We have shown, in particular, that the number of non-equilibrium quasiparticles on the island grows with the
pumping frequency as f1/2 , see Figure 19c. Considering good agreement between theory
and experiment, see Figure 19d, we conclude that the theory describes the kinetics of
non-equilibrium quasiparticles quite well.
Figure 19: (a) Schematics of the NISIN turnstile. (b) Stability diagram of the device. Red line
indicates the trajectory of the operating point while gate voltage is modulated. (c) Frequency
dependence of the number of non-equilbrium quasiparticles on the island Nqp; of the branch imbalance, i.e. of the difference between the number of electron-like and hole-like quasiparticles;
and the ratio I/ef, which characterizes the accuracy of the turnstile. (d) Fits of the experimental
dependence of the ratio I/ef on the amplitude of the gate pumping.
We have also studied Andreev 2e tunneling processes quantitatively by charge counting experiments in a SINIS structure31. We have used a single-electron transistor as an
29
Maisi, V.F., Lotkhov, S.V., Kemppinen, A., Heimes, A., Muhonen, J.T., and Pekola, J.P., Single quasiparticle excitation dynamics on a superconducting island, Phys. Rev. Lett. 111, 147001 (2013).
30
Heimes, A., Maisi, V.F., Golubev, D.S., Marthaler, M., Schön, G., and Pekola, J.P., Tunneling and
Relaxation of Single Quasiparticles in a Normal-Superconductor-Normal Single Electron Transistor,
Phys. Rev. B 89, 014508 (2014).
31
Maisi, V.F., Kambly, D., Flindt, C., and Pekola, J.P., Full counting statistics of Andreev tunneling,
Phys. Rev. Lett. 112, 036801 (2014).
Annual Report 2014
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electrometer to monitor the number of excess electrons on the N island. The applied
gate voltage has been tuned in such away that energies of charging states q = -1 or q =
+1 are the same while the state with q=0 is the ground state with the lowest energy. In
this case most of the time the system remains quiet. However, after a single-electron
tunnels, the system switches to one of the states with q = -1 or q = +1 and Andreev
tunneling becomes energetically neutral. Afterwards the avalanche process of successive Andreev tunneling is triggered. It continues until a rare single-electron event takes
the island back to the state with q =0. We have experimentally determined the full
counting statistics (FCS) of the Andreev tunneling. Due to the avalanches, we obtain
super-Poissonian statistics, see Figure 20. The bunching of the Andreev events increases
the current noise of the system.
Figure 20: Andreev avalanches in a SINIS transistor. Top left panel shows the charging energy
E for having q excess electrons on the island in Coulomb blockade. The panel below shows the
measured time trace of an electrometer, which measures the electron number on the island. It
shows single-electron and two electron-tunneling events. The single-electron event is followed
by a large number (here 16) of two-electron events. The rightmost panel presents the probability p(n,t) for observing n Andreev tunnelling events in time t = 10, 100, and 1000 ms. The dots
present experimental results and the solid lines are the corresponding theoretical results. Because of the bunching of the tunnelling events, the distributions are super-Poissonian, i.e., they
are wider than the corresponding Poissonian distributions (the dotted grey line presents the
Poisson result for t = 1000 ms).
It is crucial to be able to control the quality of the tunnel barrier between aluminum
and copper in order to improve the characteristics of SINIS single-electron turnstiles.
We have investigated the quality of the barriers in SINIS structures by means of two
methods32 (i) by comparing the rates of single electron and Andreev tunneling in the
SINIS device and (ii) by transmission electron microscopy. We have found that effective area corresponding to one conducting channel is approximately 60 times larger
than theory predicts. This discrepancy is attributed to the roughness of the tunnel barrier edges.
32
Aref, T., Averin, A., van Dijken, S., Ferring, A., Koberidze, M., Maisi, V.F., Nguyeng, H.Q., Nieminen, R.M., Pekola, J.P., and Yao, L.D., Characterization of aluminum oxide tunnel barriers by combining transport measurements and transmission electron microscopy imaging, J. Appl. Phys. 116, 073702
(2014).
Annual Report 2014
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ELECTRONIC COOLING
Anna V. Feshchenko, Jonne V. Koski, Matthias Meschke, Hung Q. Nguyen, C.
B.Winkelmann, Herve Courtois, Frank W. J. Hekking, Jukka P. Pekola, and Dmitri
Averin.
We have continued our work on on-chip electronic cooling devices, which are essential for improving the properties of sensitive low temperature radiation detectors and
other nanosized devices.
We have proposed33 and subsequently experimental realized34 an electronic cooler
based on a single electron transistor (SET), see Figure 21. It has been shown in Ref. 33
that for certain choice of bias and gate voltages applied to the SET both of its leads are
cooled. This device should have advantages over more traditional coolers based on
normal metal – insulator – superconductor (NIS) tunnel junctions at temperatures below 100 mK, where the cooling power of the latter is exponentially low. In contrast,
the cooling power of an SET cooler at low temperatures decreases much slower and
scales as T2.
Figure 21: Experimental realization of an SET cooler, Ref. 34. Left panel: schematics of the
device operation (a) and the model of the heat transfer between different parts of the device and
the substrate (b) The central island of the device has a composite normal metal – superconductor
– normal metal structure in order to thermally isolate the tow junctions. Right panel: Dependence of the temperatures of the leads on gate voltage at a fixed value of the transport voltage
V=45 mV and for two different values of the bath temperature.
We have also continued to work on further improving the electronic coolers based on
NIS junctions. A review of the recent progress in development of SINIS coolers has
been published35. In this review the effects of Andreev reflection, photonic heat
transport and phonon cooling on the performance of a cooler are discussed.
33
Pekola, J.P., Koski, J.V., and Averin, D.V., Refrigerator based on the Coulomb barrier for singleelectron tunneling, Phys. Rev. B 89, 081309(R) (2014).
34
Feshchenko, A.V., Koski, J.V., and Pekola, J.P., Experimental realization of a Coulomb blockade
refrigerator, Phys. Rev. B 90, 201407(R) (2014).
35
Courtois, H., Hekking, F.W.J., Nguyen, H.Q., and Winkelmann, C.B., Electronic Coolers Based on
Superconducting Tunnel Junctions: Fundamentals and Applications, J. Low Temp. Phys. 175, 799
(2014).
Annual Report 2014
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We have developed36 a new highly efficient SINIS cooler with the normal suspended
between the two superconducting leads, see Figure 22. The supercoducting leads are
cooled by normal quasiparticle traps of large area. The best device shows remarkable
cooling from 150 mK down to about 30 mK, a factor of 5 in temperature at a power of
40 pW.
Figure 22: SINIS cooler with suspended normal metal island and quasiparticles traps attached
to the superconducting leads (Top panel). Bottom panel – minimum temperature of the central
island reached at the optimal bias point as a function of the bath temperature for five different
samples. The inset shows the geometry of the two samples.
SQUIPT
Robab Najafi Jabdagarhi, Matthias Meschke, and Jukka Pekola
The superconducting proximity transistor was developed earlier in collaboration between PICO group and SNS Pisa37. Later it was realized that hysteresis due to loop
inductance and low responsivity due to small proximity induced gap were limiting the
performance of the device38. Recently we have demonstrated experimentally that the
hysteresis of the SQUIPT can be removed by fabricating a narrow, still short normal
link in the SQUIPT. It shows consequently almost ten times higher magnetic flux responsivity39 as compared to that in the earlier design.
36
Nguyen, H.Q., Meschke, M., Courtois, H., and Pekola, J. P., Sub-50-mK Electronic Cooling with
Large-Area Superconducting Tunnel Junctions, Phys. Rev. Appl. 2, 054001 (2014).
37
Giazotto, F., Peltonen, J.T., Meschke, M., and Pekola, J.P., SQUIPT - Superconducting Quantum Interference Proximity Transistor, Nature Phys. 6, 254 (2010).
38
Meschke, M., Peltonen, J.T., Pekola, J.P., and Giazotto, F., Tunnel Spectroscopy of a Proximity Josephson Junction, Phys. Rev. B 84, 214514 (2011).
39
Jabdaraghi, R.N., Meschke, M., and Pekola, J.P., Non-hysteretic superconducting quantum interference proximity transistor with enhanced responsivity, Appl. Phys. Lett. 104, 082601 (2014).
Annual Report 2014
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Figure 23: (a) and (b) Improved SQUIPT with a short and narrow normal link in between the superconducting leads. (c) and (d) Voltage response to magnetic field of the SQUIPT at various current bias points.
THERMOMETRY AND RADIATION DETECTION
Matthias Meschke, Jukka Pekola, Timothe Faivre, Dmitry Golubev, Christian P.
Scheller, Sarah Heizmann, Kristine Bedner, Dominic Giss, Dominik M. Zumbühl, Jeramy D. Zimmerman, and Arthur C. Gossard, F. Lombardi, T. Bauch, R. Arpaia, D.
Golubev, R. Baghdadi, M. Arzeo, G. Kunakova , S. Charpentier, S. Nawaz.
We have continued to develop and study various types of on chip thermometers with
the particular emphasis on the temperature range below 200 mK. Fast and sensitive
thermometers capable of operating at very low temperatures are required for radiation
detectors, measurements of mesoscopic quantum systems like qubits, etc. Unfortunately, at low temperatures the thermometers typically lose their sensitivity. For example,
NIS junction based thermometers are often saturated below 200 mK due to nonvanishing sub-gap conductance unless special care is taken. That is why we have continued to explore new options.
We have proposed and realized a new type of thermometer based on a superconductor
– normal metal – superconductor (SNS) Josephson junction40. Its operating principle
relies on the dependence of the critical current of the junction on the temperature of its
normal part. The latter can be very accurately monitored by collecting the switching
histograms of the junction. We have coupled two additional superconducting leads to
the normal part of the SNS junction via two tunnel junctions, thus arranging an SINIS
thermometer. The latter detects the switching of the SNS junction to the normal state,
which leads to the rise in the temperature of its normal part. In this way we have
achieved temperature resolution of 100 µK at the bath temperature 50 mK.
We have proposed a new type of silver-epoxy filters combining excellent microwave
attenuation with efficient wire thermalization, suitable for low temperature quantum
transport experiments41. The filters are made by neatly winding 2.5m of insulated Cuwire (diameter is 0.1mm) with a magnet-winding machine around a precast Ag-epoxy
rod to form a 5-layer coil. The filters are modular, of small size, robust against thermal
cycling, and possess a predictable attenuation spectrum, which can be understood as a
skin-effect filter in a lossy transmission line model. Thermometry experiments using a
GaAs quantum dot and metallic Coulomb blockade thermometers (CBTs) are em40
Meschke, M., Nanosized Electronic Cooler Combined with Superconducting Proximity Effect Thermometry, J. Low Temp. Phys. 175, 838 (2014).
41
Scheller, C.P., Heizmann, S., Bedner, K., Giss, D., Meschke, M., Zumbühl, D.M., Zimmerman, J.D.,
and Gossard, A.C., Silver-epoxy microwave filters and thermalizers for millikelvin experiments, Appl.
Phys. Lett. 104, 211106 (2014).
Annual Report 2014
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ployed to investigate the filter performance, demonstrating CBT electron temperatures
down to 7.5 mK, see Figure Figure 24.
Figure 24: Electron temperature Te extracted from GaAs dot current and conductance measurements as
indicated versus refrigerator temperature TMC, with dashed line showing ideal thermalization Te=TMC.
The upper inset shows a typical zero-bias peak at base temperature with cosh-2 fit. Right inset: photo of
a filter (22mm long, 5mm diameter) with centimeter scale bar. Lower inset: micrograph of a quantum
dot. Gates N, L, R, and P (light grey) form the dot. Dark gates are grounded.
We have developed a thermometer based on SIS’IS structure, which is a combination
of two Josephson junctions connected in series42. The outer superconducting leads are
made of aluminum, while the inner island is made of titanium with the critical temperature TC=315 mK. At temperatures higher that TC it is an SINIS structure with very
high zero bias resistance. In contrast, below TC the structure has high Josephson critical current and zero resistance. In the narrow temperature interval around TC zero bias
resistance changes by several orders of magnitude, which makes the device a very sensitive thermometer in this temperature range. We have proposed to use it as a detector
of radiation in the same way as transition edge sensors, in which SS’S with good contacts between superconductors are typically used43. Our device has the temperature
sensitivity at the level 2*10-6 K/Hz1/2.
We have proposed to use the effect of disorder enhanced Andreev reflection for the
low temperature thermometry44. We have fabricated and SINIS structure with relatively transparent tunnel junctions, in which case higher corrections to the tunnel current
42
Faivre, T., Golubev, D., and Pekola, J.P., Josephson junction based thermometer and its application
in bolometry, J. Appl. Phys. 116, 094302 (2014).
43
Karasik, B.S., Sergeev, A.V., and Prober, D.E., Nanobolometers for THz photon detection, IEEE
Trans. Terahertz Sci. Technol. 1, 97 (2011).
44
Faivre, T., Golubev, D.S., and Pekola, J.P., Andreev current for low temperature thermometry, Appl.
Phys. Lett. 106, 182602 (2015).
Annual Report 2014
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result in a narrow peak in differential resistance around zero bias45, which corresponds
to a step in the I-V curve, Figure Figure 25. As a result, zero bias resistance of the device
has non-monotonous temperature dependence: with lowering temperature it first grows
exponentially, as expected for a highly resistive SINIS structure, but then, instead of
saturating, it reaches the maximum and drops to much lower values, see the right panel
of Figure Figure 25. We propose to use this effect to measure the temperature. In our
device we have achieved the sensitivity of 4.3 MΩ/K in the temperature range from 80
mK to 200 mK.
Figure 25: Left panel – I-V curve of the SINIS structure. Top inset – sample image, lower inset –
zoom of the I-V curve at low bias. Right panel – temperature dependence of zero bias resistance.
Inset – zoom of the lower temperature part of the curve.
In collaboration with Chalmers University of Technology we have studied the properties of high-TC nanowires made of YBCO and considered their potential applications
as radiation detectors. We have shown, in particular, that the formation of a hot spot in
the wire, caused, for example, by an absorbed photon, proceeds differently than in traditional detectors based on niobium nitride nanowires46. The difference originates
from high critical current density of YBCO as well as unusual temperature dependence
of its thermal conductivity. We have also studied in detail the superconducting phase
transition in YBCO nanowires47. We have shown that the smearing of the temperature
dependence of zero bias resistance below the critical temperature is caused by vortex
entry events, in agreement with the theory.
Starting from the London-type model, we study the domain structures in ferromagnetic
superconductors taking account of the nucleation of vortices and antivortices coupled
to themagnetic texture.We predict that the coupling between domains and vortices results in the formation of two energetically favorable domain configurations: (i) a
Meissner-type vortex-free configuration with strong domain shrinking and (ii) a more
rare domain configuration with a dense vortex-antivortex lattice. The switching be45
Hekking, F.W.J., and Nazarov, Yu.V.., Interference of two electrons entering a superconductor, Phys.
Rev. Lett. 71, 1625 (1993).
Golubev, D., Lombardi, F., and Bauch, T., Effect of heating on critical current of YBCO nanowires, Physica C 506, 174 (2014).
46
47
Arpaia, R., Golubev, D., Baghdadi, R., Arzeo, M., Kunakova, G., Charpentier, S., Nawaz, S., Lombardi, F., and Bauch, T., Resistive state triggered by vortex entry in YBa2Cu3O7- nanostructures, Physica C 506, 165 (2014).
δ
Annual Report 2014
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tween these configurations is shown to result in the first-order phase transitions, which
could be observable in superconducting uranium-based compounds48.
We have continued our work on fast electron thermometry49. Our detection technique
is based on the temperature dependent conductance of a NIS junction. In order to enable a fast readout we have embedded it in an LC resonant circuit. In the first generation
of the device we have achieved 90 µK/Hz1/2 noise-equivalent temperature with 10
MHz bandwidth. Such a calorimetric detector, upon optimization, can be seamlessly
integrated into superconducting circuits, with immediate applications in quantum
thermodynamics experiments down to single quanta of energy.
48
Khaymovich, I.M., Mel’nikov, A.S., and A.S. Buzdin, A.S., Phase transitions in the domain structure
of ferromagnetic superconductors, Phys. Rev. B 89, 094524 (2014).
49
Gasparinetti, S., Viisanen, K.L., Saira, O.-P., Faivre, T., Arzeo, M., Meschke, M., and Pekola, J.P.,
Fast Electron Thermometry for Ultrasensitive Calorimetric Detection, Phys. Rev. Appl. 3, 014007
(2015).
Annual Report 2014
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ROTA group
Samuli Autti, Vladimir Eltsov, Petri Heikkinen, Risto Hänninen, Niklas Hietala, Matti Krusius, Jere Mäkinen, and Vladislav Zavjalov
Visitors and Collaborators: A.W. Baggaley (University of Glasgow, UK), V.V.
Dmitriev (Kapitza Institute, Russia), R.P. Haley (University of Lancaster, UK), V.S.
L’vov (Weizmann Institute, Israel), M. Silaev (Royal Institute of Technology, Sweden), and G.E. Volovik (Aalto University)
The research in the ROTA group in recent years has been focused on the properties of
superfluid 3He at ultra-low temperatures. We are interested in the superfluid phases of
3
He as the best examples of topological superfluids, which share many properties with
popular topological insulators and superconductors. One of these properties is emergent fermion zero modes, like Majorana fermions at the surfaces and in the cores of
the topological defects. Superfluid phases of 3He also possess a rich variety of bosonic
collective modes, including analogous of the Higgs boson. We are using Bose-Einstein
condensates of magnon quasiparticles, trapped within the superfluid, as a probe for
these fermionic and bosonic excitations. We have studied relaxation of such condensates in a wide range of rotation velocities, temperatures, pressures and magnetic
fields. The identification of various relaxation mechanisms is a work-in-progress. In
year 2014 we, in particular, elucidated the relaxation channel connected to parametric
excitation of light Higgs boson mode.
Another area of our research is the exploration of dynamic properties of the fermionic
superfluid in the zero-temperature limit. In year 2014 we have extensively studied a
new type of quantum turbulence: Turbulence of inertial and Kelvin waves in a vortex
cluster in rotating superfluid. In this system vortex reconnections are substantially
suppressed, compared to usual realizations of hydrodynamic quantum turbulence,
where reconnections play an essential role. This allows us to concentrate on dynamics
of vortex waves. From the measurement of dissipation in wave turbulence at temperatures below 0.15Tc we have found the first experimental evidence for the Kelvin-wave
cascade.
DECAY OF MAGNON BEC VIA LIGHT HIGGS CHANNEL
V.V. Zavjalov, S. Autti, V.B. Eltsov, P.J. Heikkinen, G.E. Volovik
Symmetry breaking in 3He-B has many common features with the symmetry breaking
in particle physics. There are 18 collective modes of the order parameter in 3He-B, of
which 14 are the high-energy amplitude modes – analogs of the heavy Higgs bosons,
and 4 are the low-energy Nambu-Goldstone (NG) bosons (sound wave plus three spin
wave modes). One of the spin wave modes acquires small mass due to a tiny spin-orbit
interaction. It becomes equivalent to the light Higgs boson in the composite Higgs
scenarios, which are suggested, in particular, to explain the relatively small mass of the
Higgs boson discovered at the LHC. In applied magnetic field, the other two spin
wave modes split into the gapped mode (magnon, or optical magnon) and the gapless
NG mode with the quadratic dispersion (acoustic magnon), Figure 26 (right). We have
performed the first experimental observation of resonant parametric decay of a BoseEinstein condensate of optical magnons into pairs of light Higgs bosons and into pairs
Annual Report 2014
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of acoustic magnons.50 In addition we can see a direct transition between optical and
acoustic magnons, mediated by rotation of non-axisymmetric cores of quantized vortices.
Figure 26: (Left) Setup for measurements of the decay of trapped Bose-Einstein condensates of magnons in superfluid 3He-B. The nearly harmonic trapping potential U (blue lines in the plots) in the radial
direction is formed by the cylindrically symmetric ''flare-out'' texture of the orbital anisotropy axis of the
order parameter (green arrows). The trap in the axial direction is formed by the spatial variation of magnetic field produced by the pinch coil. Red curves show amplitude of the magnon BEC wave function in
the trap. (Right) Observed decay channels of the magnon BEC shown as arrows on the spectra of the
spin-waves modes in 3He-B.
In superfluid 3He-B harmonic 3-dimensional potential traps for magnon quasiparticles
can be created within 3He bulk using combined effect of the orbital order-parameter
texture and applied profile of the magnetic field, Figure 26 (left). With a pulse in the
NMR coils incoherent magnons with energies above the ground level in the trap are
pumped into the system. If the density of pumped magnons is sufficient for effective
magnon-magnon interaction, then within about 0.1 s they relax to the ground level and
form a spontaneously coherent condensate. Magnon condensation is manifested by
coherent precession of the magnezation, which is monitored by the NMR spectrometer. The signal amplitude is proportional to the average tipping angle of the magnetization in the condensate.
When the number of magnons in the condensate is relatively small, then it decays via
spin diffusion in the normal component and via losses in the NMR pick-up circuit.51
At temperatures of our measurements, below 0.15Tc, the decay time of the condensate
reaches minutes. We have found that if the number of magnons in the condensate (and
thus the tipping angle of the magnetization and the amplitude of the NMR signal) exceed some threshold, then the decay becomes orders of magnitude faster, than predicted by the aforementioned mechanisms, Figure 27 (lower inset). We explain this observation using known Suhl instability of coherent precession. In this process a magnon
with energy ωL splits to two other spin-wave modes with energy ωL/2 and opposite
50
Zavjalov, V.V., Autti, S., Eltsov, V.B., Heikkinen, P.J., and Volovik, G.E., Light Higgs channel of the
resonant decay of magnon BEC in superfluid 3He-B, [arXiv:1411.3983].
51
Heikkinen, P.J., Autti, S., Eltsov, V.B., Hosio, J.J., Krusius, M., and Zavjalov, V.V., Relaxation of
Bose-Einstein condensates of magnons in magneto-textural traps in superfluid 3He-B, J. Low Temp.
Phys. 175, 3 (2014).
Annual Report 2014
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momenta +q and −q. The larger the probability of such decay, the smaller is the
threshold amplitude.
Figure 27: Suhl instability in the decay of magnon
BEC. (Lower inset) Down to certain threshold amplitude the decay of the condensate is substantially
faster. This threshold is inversely proportional to
the rate of parametric excitation of other spin-wave
modes. (Main panel) Threshold amplitude as a
function of precession frequency ωL/2π at three
pressures shows step-like decrease when the light
Higgs channel of decay opens at ωL>2ΩB. (Upper
inset) Superimposed on the frequency dependence
is periodic variation of the threshold corresponding
to parametric decay to closely spaced acoustic
magnon resonances in our cylindrical sample.
In 3He-B there are two possibilities for the decay products, Fig.Figure 26 (right). One
possibility is a spin-wave mode, which acquires mass due to spin-orbit interaction.
This mode plays a role of the light Higgs boson. The mass of the boson is given by the
Leggett frequency ΩB. Thus, this decay channel is available only if ωL ≥ 2ΩB. In the
experiment we indeed observe that the threshold of the Suhl instability sharply drops
when ωL is increased above 2ΩB, Figure 27.
Another possibility for the decay products is the gapless acoustic magnons, for which
our cylindrical container forms a resonator. Frequencies in our experiment correspond
to wavelength of acoustic magnons of the order of 10-3 of the diameter of the sample.
Thus acoustic-magnon resonances are closely spaced on the frequency scale. Nevertheless, they are clearly observed in the experiment, Fig. Figure 27 (upper insert). Owing to the short wavelength, it is practically impossible to excite acoustic magnons directly in a typical NMR experiment. Our indirect observation is the first confirmation
of their existence.
WAVE TURBULENCE AND THE KELVIN-WAVE CASCADE
J. Mäkinen, S. Autti, V.B. Eltsov, P.J. Heikkinen, R. Hänninen, M. Krusius, V.S.
L'vov, V.V. Zavjalov
In steady rotation superfluids mimics solid-body rotation by forming an array of quantized vortex lines oriented along the axis of rotation, which is parallel to the axis of our
cylindrical sample. In this vortex array vortices can oscillate around the equilibrium
position. These excited modes are called vortex waves. At long wavelength, larger
than the intervortex distance, vortex waves mimic inertial waves of classical ideal fluid. At shorter wavelength vortex tension becomes important and vortex waves are
Kelvin waves. In our setup all walls of the sample container are smooth except the bottom surface where vortices are pinned. When the angular velocity of rotation Ω is
Annual Report 2014
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modulated at low temperatures, where the mutual friction is low, vortex lines in bulk
cannot follow the motion of the pinned ends and thus are periodically stretched. This
pumps the energy into the system of vortex waves. The pumping scale is determined
by the period of the modulation and for our experiments the wavelength is of a few
centimeters, well in the inertial-wave regime.
The response of the vortex cluster to the excitation is monitored by measuring the
NMR signal of the magnon BEC immersed in the vortex cluster. Such condensate is
not only a sensitive thermometer, but also a tool to observe the dynamics of the orderparameter texture,52 which in turn is affected by the polarization of vortex lines. The
largest contribution to the observed signal comes from the scales of the intervortex distance. By pumping inertial waves at large scales and observing decrease of polarization at a scale where they transform to Kelvin waves, we prove that there is a cascade
of inertial waves in our ultra-low temperature superfluid.
After stopping the pumping, we observe a two-stage relaxation process, Figure 28. In
the first stage, of length t0, energy of large-scale flow (inertial waves and additionally
created solid-body rotating flow) is dissipated while the vortex polarization, determined by Kelvin waves remains low. The rate of this dissipation is temperatureindependent, which confirms the picture of the energy cascade at large scales.
Figure 28: Relaxation of wave turbulence in superfluid 3He-B at ultra-low temperatures. (Left) Periodic
modulation of the angular velocity Ω excites inertial-wave turbulence at scales larger than the intervortex distance and Kelvin-wave turbulence at smaller scales. After stopping the modulation the turbulence
decays in two-stage relaxation process, as seen in the NMR measurements of vortex polarization.
(Right) Dependence of the effective friction parameter for the Kelvin waves (symbols), extracted from
the relaxation time τ, on the mutual friction parameter α(T) shows transition from damping of individual
Kelvin waves at α > 10-4 to the temperature-independent damping from the Kelvin-wave cascade at
smaller α. The solid line is 2α.
The second stage, relaxation of polarization with characteristic time τ, measures the
decay of Kelvin waves. It is expected that at higher temperatures and larger mutual
friction values the dissipation of Kelvin waves is mutual-friction dominated and τ is
proportional to α-1. At low temperatures the operation of the Kelvin-wave energy cascade is expected, which should result in the temperature-independent dissipation. Despite the central role ascribed to the Kelvin-wave cascade in theoretical description of
quantum turbulence in the zero-temperature limit, its existence has not been proven so
far. There is weak evidence from numerical simulations, but no experimental support.
52
Heikkinen, P.J., Autti, S., Eltsov, V.B., Haley, R.P., and Zavjalov, V.V., Microkelvin thermometry
with Bose-Einstein condensates of magnons and applications to studies of the AB interface in superfluid
3He, J. Low Temp. Phys. 175, 681 (2014).
Annual Report 2014
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We can extract effective friction for Kelvin waves αeff from the relaxation time τ and
compare it to the independently in-situ measured values of the mutual friction coefficient α(T), as shown in Figure 28 (right). We find that at higher temperatures indeed
αeff ≈ α, while at the lowest temperatures αeff ≈ const. The change of behavior occurs at
α ~ 10-4, which agrees with the theoretically expected threshold for suppression of the
Kelvin-wave cascade by friction. We thus consider our measurements as the first experimental evidence for the Kelvin-wave cascade.
53
At even higher temperatures than shown in Fig. Figure 28 (right) the dependence of the
damping on temperature changes again, which may be connected to the so-called decoupling transition, discovered by us earlier.54 This transition is a result of the competition in vortex dynamics between the vortex-tension-dominated and the mutualfriction-dominated behavior.
VORTEX DYNAMICS AT LOW TEMPERATURES AND FORMATION OF
COHERENT VORTEX STRUCTURES
R. Hänninen and N. Hietala
While the mechanisms for energy dissipation in the zero temperature limit are one of
the central problems in the research of quantum turbulences, another important topic is
the similarity of quantum turbulence with its classical counterpart. One question is
whether a tangle of quantized vortices is able to form different sizes of eddies by forming vortex bundles, and whether a classical Richardson-Kolmogorov energy cascade
realizes on scales larger than the average intervortex distance. This cascade could then
feed the Kelvin-wave cascade that is predicted to appear at smaller scales.
In numerical simulations of vortex dynamics we have observed vortex bundling and
the appearance of coherent vortex motion during a transition period when a vortex
tangle in superfluid 3He-B relaxes to its new equilibrium state after a change of the
driving force.55 One example of the coherent motion is the decay of vortex array in a
cubical geometry at low temperature about 0.2Tc. At the early stages of this decay, helical type distortions appear on the vortices. This coherent motion might be related to
the lowest inertial wave resonances and is illustrated on the left part of Figure 29. In
this figure, the coherent structures are identified by applying a Gaussian type smoothing to the vorticity, and then color coding the local smoothed vorticity. The coherent
structures are those where the vorticity substantially exceeds its root mean square value.
Even more clear appearance of the vortex bundles occurs during the formation of the
vortex array from multiplication of a seed vortex. The right part of Figure 29 illustrates
the vortex configurations in a cylinder that is tilted by 30 degrees with respect to the
rotation axis. In the case of T=0 only numerical dissipation exists, and even a single
seed vortex eventually generates a vortex array. The vortex number increases due to
vortex-vortex reconnections, and especially due to reconnections with the cylinder
Eltsov, V.B., Hosio, J.J., Krusius, M., and Mäkinen, J., Andreev reflection in rotating superfluid 3HeB, JETP 119, 1069 (2014).
53
54
Eltsov, V.B., Hänninen, R., and Krusius, M., Quantum turbulence in superfluids with wall-clamped
normal component, Proc. Natl. Acad. Sci. USA 111, 4711 (2014).
55
Hänninen, R., and Baggaley, A.W., Vortex filament method as a tool for computational visualization
of quantum turbulence, Proc. Natl. Acad. Sci. USA 111, 4667 (2014).
Annual Report 2014
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boundary. However, before the array settles down to steady-state, two vortex clusters
appear that both consist of around dozen single quantum vortices, as seen on Figure 29.
These simulations show that the vortex bundling in the superfluid component is not
such a rare phenomenon, and that it does not necessarily need normal fluid, or vorticity
(vortex bundles) in the normal component, to appear. Rather, the superfluid component may mimic the normal fluid component by itself.
Figure 29: (Left) Decay of vorticity in superfluid 3He-B after a sudden stop of rotation from Ω = 0.5
rad/s. The initial state inside the cube (side 6 mm) was a steady-state vortex array, with a small tilt to
break the symmetry. The main figure illustrates only the coherent part at t = 87 s where the smoothed
vorticity ω > 1.4ωrms. The temperature here is 0.20Tc. The full vortex configuration is given below, together with a coherent part configuration obtained from similar simulations at slightly higher temperature, T = 0.22Tc and t = 64 s. Colors show the magnitude of the smoothed vorticity. (Right) Coherent
structures appearing in a tilted cylinder during the spin-up of the superfluid component at T = 0. The
cylinder has a radius of 3 mm and height of 5 mm. The rotation velocity is 0.25 rad/s and the subfigures for the full vortex configuration correspond to times 1100 s, 1130 s, 1140 s, and 1150 s. The
coherent structure at 1140 s is illustrated at the bottom. The temporal evolution of the vortex line density, L (solid blue line), together with the rms (dashed red line) and maximum vorticity (solid red line) is
shown in the bottom-right sub-figure.
Annual Report 2014
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µKI group
Miika Haataja, Matti Manninen, Antti Ranni, Tapio Riekki, Juho Rysti, Alexander
Sebedash, Igor Todoshchenko, and Juha Tuoriniemi
Collaborators: Jukka-Pekka Kaikkonen and Alexander Savin
The research work of the µKI group is focused on interacting fermions in natural condensed matter systems at very low temperatures, where coherent quantum effects come
into play. More specifically, we study the properties of 3He in its naturally occurring
states in pure liquid phase, solid phase, and diluted phases in mixtures with 4He. Mixtures of 3He and 4He provide a rich system in their liquid and solid forms with yet unexamined regions in their phase space. Most notably, the superfluid state of dilute 3He
in 4He is yet to be experimentally reached, whereas there are firm theoretical predictions about its existence at yet unknown low temperatures. We develop new cooling
methods to extend the regime accessible for experimental investigations. In pure 3He
we study the interface phenomena on free surface of liquid and on the interface between solid and superfluid 3He. There are new undiscovered phenomena expected to
occur on such interfaces. The main objective here is to discover crystallization waves
on the liquid-solid interface of 3He at very low temperatures.
These tasks require most advanced cooling techniques, which go even beyond the already established nuclear-demagnetization refrigeration used to provide temperatures
in the microkelvin regime. Our multi-stage refrigerator is one of the most powerful
units of its kind worldwide, and it is well equipped to host complex experiments like
those mentioned above.
FREE SURFACE OF SUPERFLUIDS
Matti Manninen, Antti Ranni, Juho Rysti, Igor Todoshchenko, and Juha Tuoriniemi
The ample data produced by our measurements on the surface waves on both superfluids 3He and 4He from our previous cooldown have been further processed to gain understanding and illustrate some fundamental properties of these exotic media and hydrodynamics in general. Attenuation of such waves at very low temperatures is due to
ballistic quasiparticles, which have a fundamentally different character in the bosonic
superfluid 4He and in the fermionic 3He. This matter was discussed in detail in the
publication by Manninen et al.56 The standing wave mode frequencies on the free surface depend on the kinetic, potential, and surface energies, and can be measured with
good precision. We observed few dozen such modes on the superfluid surfaces with
varying depth of fluid in the experimental cell. The analysis of that has been carried
further. These matters will be discussed in a forthcoming publication and in the PhD
thesis by Matti Manninen. No full understanding of all our observations has emerged
yet, and the work will be continued by performing full 3D simulations of the problem.
SECOND SOUND IN HELIUM MIXTURES
Matti Manninen, Tapio Riekki, Juho Rysti, and Juha Tuoriniemi
Our work on isotopic helium mixtures has been continued by investigating the coupling between the first and second sound in the dilute 3He – superfluid 4He solutions.
56
Manninen, M., Rysti, J., Todoshchenko, I., and Tuoriniemi, J., Quasiparticle damping of surface
waves in superfluid 3He and 4He, Phys. Rev. B90, 224502 (2014).
Annual Report 2014
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Mechanical oscillators, in particular the now so popular quartz tuning forks, used for
probing the properties of helium fluids at very low temperatures have been observed to
be influenced by the acoustic properties of the medium.57 This is especially important
in helium mixtures, where the second sound velocity is in the range prone to create
standing second sound resonances within typical experimental geometries. The coupling of those to the quartz tuning fork resonator is not a direct process but requires
also the coupling between the first and second sound. Our theoretical analysis suggested, that there may be a complete compensation of two terms contributing to this coupling at certain values of the 3He concentration and temperature, so that no coupling at
all would then remain.58 Recently we have confirmed experimentally that this indeed
is the case. Detailed analysis of this phenomenon may be used to deduce some of the
involved system properties with improved accuracy.
DRY NUCLEAR DEMAGNETIZATION REFRIGERATOR
Miika Haataja, Pertti Hakonen, Jukka-Pekka Kaikkonen, Alexander Savin, and Igor
Todoshchenko
The group working on Dry Demag cryostat had two short-term (for about one year)
and two long-term projects. The first short-term project was to demonstrate for the first
time the adiabatic nuclear demagnetization cooling well below 1 mK in helium-free
cryostat with Pulse-tube pre-cooler. The base of the cryostat is commercial BF-LD400
dry dilution cryostat from BlueFors Cryogenics. BlueFors Cryogenics, Ltd., is a company, which arose from the OVLL where many former students and postdocs from
OVLL are working, and the company has long and successful collaboration with the
Lab.
One of the spectacular result of this collaboration is Dry Demag cryostat where cooling of 3He deep to the superfluid state has been achieved in February, 2014 for the first
time. The most essential problem in cooling was mechanical vibrations coming from
the Pulse-tube precooler. Dry dilution cryostats like BF-LD400 have a lot of advantages compared to usual liquid helium cryostats as they don't require regular helium transfer and are much easier to operate, but the mechanical vibration is their essential disadvantage. Vibrations are detrimental for demagnetization cooling because they
result in strong eddy currents which heat the copper nuclear stage, and that is why it
was important to demonstrate still the possibility of nuclear cooling in such dry cryostats. A lot of efforts have been applied to reduce the oscillations, and the most important improvement was the spacers between nuclear stage and the 9 T superconducting solenoid, which kept the stage and the magnet strongly tighten mechanically, so
that they vibrated together without significant relative movement. After the spacers
were introduced, the temperature of 160 µK has been reached in liquid 3He in the cell,
which was a part of the copper nuclear stage. Cooling helium down to 160 µK is a
very good result even for usual large helium cryostats as only few experimental groups
in the world could reach such low temperatures. In Dry Demag cryostat helium was
kept at this lowest achievable temperature for several hours, while the temperature of
700 µK (still in the superfluid state) can be kept for 16 hours. The pre-cooling time is
57
Rysti, J. and Tuoriniemi, J., Quartz Tuning Forks and Acoustic Phenomena: Application to Superfluid
Helium, J. Low Temp. Phys., 177, 133-150 (2014).
58
Rysti, J., Microscopic and Macroscopic Studies of Liquid and Solid Helium Mixtures, Thesis, Aalto
University, School of Science, O.V. Lounasmaa Laboratory (2013).
Annual Report 2014
– 55 –
less than two days. The temperature of helium has been measured with the oscillating
fork whose damping is proportional to the number of quasiparticles. We have suggested and demonstrated the easy and natural way to calibrate the fork at the temperature
of the crossover from hydrodynamic to ballistic regime of collisions with quasiparticles.
With this experimental cell we are planning to investigate the waves on helium surfaces, which is the first long-term project. We will start with experiments on waves on
free surface of superfluid 4He and 3He and the final goal is to observe crystallization
waves on liquid-solid interface of 3He. Two capacitors (one to excite the waves and
another one to detect them) have been made from superconducting wires of 50 µm diameter wounded bifilarly on copper holders. In this way we hope to avoid strong heating due to dielectric losses, which are large in usually used interdigital capacitors
drawn on quartz (sapphire) substrate. The measurement capacitor is incorporated into a
high-Q resonant circuit along with a 1 mH inductance also wound with superconducting wire. The resonance frequency of the circuit of about 1 MHz will be oscillating
with the frequency of standing surface waves of about 30 Hz, which will be seen as
change of the amplitude of 1 MHz oscillation, when staying on the steep wing of the
resonance. In order to increase the Q-factor of the resonance and to avoid cross-talking
of the lines, we have made superconducting coaxes instead of resistive twisted pairs
originally present in the cryostat.
Another project running on the Dry Demag cryostat is the suspended carbon nanotube.
The aim of the project is to observe and investigate the interaction of mechanical oscillations of the nanotube with the surface states of superfluid helium. As a short-term
project in this frame we have demonstrated that it is possible to merge the tube in helium without breaking it by cooling the cell with helium at the pressure slightly higher
than the critical pressure of helium. In this way there is no helium liquid-gas interface
during the whole course of cooling.
Annual Report 2014
– 56 –
THEORY group
Tero Heikkilä, Ville Kauppila, Raphaël Khan, Teemu Ojanen, Kim Pöyhönen, Joel
Röntynen, Mikhail Silaev, Pauli Virtanen, Grigori Volovik, and Alex Westström
Visitors: Pablo Esquinazi, Gil Jannes, Victor Khodel, Toru Matsuura, Vladimir Mineev, Hiroyoshi Nobukane, Satoshi Tanda, and Dmitrii Tayurskii.
Collaborators: Sebastian Bergeret (San Sebastian, Spain), Kjetil Börkje (Nils Bohr
Institute, Copenhagen), Pablo Equinazi (Leipzig University, Germany), Tero Heikkilä
(University of Jyväskylä), Francesco Giazotto (CNR NANO and Scuola Normale Superiore, Italy), Mikhail Katsnelson (Radboud University Nijmegen, The Netherlands),
Yuriy Makhlin (Landau Institute, Russia), Asier Ozaeta (San Sebastian, Spain), Benedikt Probst (TU Braunschweig, Germany), Patrick Recher (TU Braunschweig, Germany), Mikhail Silaev (KTH, Sweden), Dmitrii Tayurskii (Kazan Federal University,
Russia), Erkki Thuneberg (University of Oulu), Mike Zubkov (The University of
Western Ontario, Canada).
The year 2014 was another year of changes in Theory group. After the move of Tero
Heikkilä to the University of Jyväskylä in 2013 (part time in Lounasmaa laboratory
until June 2014), our recruitment of a new professor in theoretical condensed matter
physics of quantum phenomena and devices was completed. PhD Christian Flindt was
assigned to assistant professorship starting in February 2015.
The following list of projects describes our activities in 2014.
SPIN EFFECTS IN ZEEMAN-SPLIT SUPERCONDUCTORS
Pauli Virtanen, in collaboration with M. Silaev, T.T. Heikkilä, and F.S. Bergeret
We present59 a theoretical study of spin transport in a superconducting mesoscopic
spin valve under the action of a magnetic field misaligned with respect to the injected
spin. We demonstrate that superconductivity can either strongly enhance or suppress
the coherent spin rotation, depending on the type of spin relaxation mechanism being
dominated either by spin-orbit coupling or spin-flip scattering at impurities. We also
describe60 the far from equilibrium non-local transport in a diffusive superconducting
wire with a Zeeman splitting, taking into account the different spin relaxation mechanisms. We demonstrate that due to the Zeeman splitting an injection of a current in a
superconducting wire creates a spin accumulation that can only relax via thermalization.
59
Silaev, M., Virtanen, P., Heikkilä, T.T., and Bergeret, F.S., Spin Hanle effect in mesoscopic superconductors, Physical Review B, 91, 024506 (2015).
60
Silaev, M., Virtanen, P., Bergeret, F.S., and Heikkilä, T.T., Long-Range Spin Accumulation from
Heat Injection in Mesoscopic Superconductors with Zeeman Splitting, Physical Review Letters, 114,
167002 (2015).
Annual Report 2014
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CONTROLLING SPIN POLARIZATION OF A QUANTUM DOT VIA A
HELICAL EDGE STATE
Pauli Virtanen, in collaboration with B. Probst and P. Recher
We investigate61 a Zeeman-split quantum dot (QD) containing a single spin 1/2 weakly
coupled to a helical Luttinger liquid (HLL) within a generalized master equation approach. The HLL induces a tunable magnetization direction on the QD controlled by
an applied bias voltage when the quantization axes of the QD and the HLL are noncollinear.
THERMAL TRANSPORT PROPERTIES OF JOSEPHSON WEAK LINKS
Pauli Virtanen, in collaboration with F. Giazotto
We discuss62 how phase coherence manifests in the heat transport through superconducting single and multichannel Josephson junctions in time dependent situations. We
consider the heat current driven through the junction by a temperature difference in dc
voltage and ac phase biased situations. We also discuss63 the statistics of heat current
between two superconductors at different temperatures connected by a generic weak
link. As the electronic heat in superconductors is carried by Bogoliubov quasiparticles,
the heat transport fluctuations follow the Levitov-Lesovik relation. We identify the
energy-dependent quasiparticle transmission probabilities and discuss the resulting
probability density and fluctuation relations of the heat current.
MICROWAVE NANOBOLOMETER BASED ON PROXIMITY JOSEPHSON
JUNCTIONS
Pauli Virtanen, in collaboration with J. Govenius, R.E. Lake, K.Y. Tan, V. Pietilä, J.K.
Julin, I.J. Maasilta, and M. Möttönen
We introduce64 a microwave bolometer aimed at high-quantum-efficiency detection of
wave packet energy within the framework of circuit quantum electrodynamics, the ultimate goal being single microwave photon detection. By measuring the differential
thermal conductance of the same bolometer design in qualitatively different environments and materials, we determine that electron-photon coupling dominates the thermalization of our nanobolometer.
61
Probst, B., Virtanen, P., and Recher, P., Controlling spin polarization of a quantum dot via a helical
edge state, [arXiv:1407.3253].
62
Virtanen, P., and Giazotto, F., Thermal transport through ac-driven transparent Josephson weak
links, Physical Review B, 90, 014511/1-12 (2014).
63
Virtanen, P., and Giazotto, F., Fluctuation of heat current in Josephson junctions, AIP Advances, 5,
027140 (2015).
64
Govenius, J., Lake, R. E., Tan, K. Y., Pietilä, V., Julin, J. K., Maasilta, I. J., Virtanen, P., and Möttönen, M., Microwave nanobolometer based on proximity Josephson junctions, Physical Review B, 90,
p. 064505 (2014).
Annual Report 2014
– 58 –
GROUND STATE COOLING OF MECHANICAL MOTION IN THE
UNRESOLVED SIDEBAND REGIME BY USE OF OPTOMECHANICALLY
INDUCED TRANSPARENCY
Teemu Ojanen, in collaboration with K. Börkje
Anticipating the experimental breakthrough in topological superconductivity in magnetic chains on top of a superconductor, theoretical studies of such systems was initiated65. In the study it was established that multiple Majorana end states can be stabilized
in simple coupled chains and ladders. These Majorana bound states can be directly observed by using STM spectroscopy methods.
TUNING TOPOLOGICAL SUPERCONDUCTIVITY IN HELICAL SHIBA
CHAINS BY SUPERCURRENT
Joel Röntynen and Teemu Ojanen
In our study66 we pointed out that the topological superconducting state in helical
magnetic chains can be tuned by applying supercurrents flowing in the underlying superconductor. If such systems can be realized, the supercurrent can be employed in
moving the Majorana states. The subsequent observation of topological superconductivity by the Princeton group in the late 2014 has increased the attention towards the
magnetic systems.
MAJORANA STATES IN HELICAL SHIBA CHAINS AND LADDERS
Kim Pöyhönen, Alex Westström, Joel Röntynen and Teemu Ojanen
Cooling of mechanical motion to its quantum mechanical ground state was studied67.
The main motivation was to device cooling technique in an optomechanical setup,
which does not allow standard resolved side-band cooling. We introduced new techniques employing auxiliary mechanical degrees of freedom that could be employed in
the cooling process. The resulting paper was elected as to Editor's Suggestion category.
QUANTUM FIELD THEORIES AND SUPERFLUID 3HE
Grigory Volovik
BACKGROUND
Physics of superfluid 3He influences the development of many other areas of physics.
The main reason for that is that phases of superfluid 3He belong to the so-called topological media68. Topological media are systems whose properties are protected by to65
Ojanen, T., and Borkje, K., Ground-state cooling of mechanical motion in the unresolved sideband
regime by use of optomechanically induced transparency, Physical Review A, 90, 013824 (2014).
66
Röntynen, J., Ojanen, T., Tuning topological superdoncuctivity in helical Shiba chains by supercurrent, Physical Review B, 90, 180503(R) (2014).
67
Pöyhönen, K., Westsröm, A., Röntynen, J., and Ojanen, T., Majorana states in helical Shiba chains
and ladders, Physical Review B, 89, p. 115109 (2014).
68
Volovik, G.E., From Standard Model of particle physics to room-temperature superconductivity,
submitted to proceedings of Nobel Symposium 156 "New forms of Matter - Topological Insulators and
Superconductors", [arXiv:1409.3944].
Annual Report 2014
– 59 –
pology, and thus do not depend on the details of interaction and are robust to deformations of the system. The broad class of topological matter is characterized by topologically stable Fermi points (Weyl, Dirac and Majorana points) in the excitation spectrum. The main property of media with the point nodes is the phenomenon of emergent
physical laws. Close to the Weyl point, the fermionic and bosonic degrees of freedom
are described in terms of left-handed and right-handed fermions, gauge bosons and
metric fields. This means that all the ingredients of the Standard Model of particle
physics and gravity may naturally emerge together with the effective relativistic invariance, gauge invariance, relativistic spin and other physical laws. This suggests the
new paradigm that the quantum vacuum of the Standard Model also belongs to the
topological media, and the physical laws which we have in our Universe are the emergent phenomena, which are the natural properties of the topological media of a given
universality class. The best representative of the universality class, which shares the
properties of the quantum vacuum of particle physics in its massless phase, is the chiral phase of superfluid 3He, called 3He-A. Superfluid 3He-A experiences the phenomenon of chiral anomaly, which is manifested in the Kopnin force acting on vortexskyrmions and in observed chiral magnetic effect, which is now under intensive investigation in quantum chromodynamics. The other condensed matter topological media,
which have topologically protected Dirac or Weyl points and thus share some properties of superfluid 3He and quantum vacuum, include graphene, chiral superconductors,
topological Weyl and Dirac semimetals, cuprate superconductors, and some states of
the ultracold gases in laser traps.
The time reversal symmetric phase of superfluid 3He, the 3He-B, is the best representative of another broad class of topological media, the topologically nontrivial fully
gapped systems. This class contains also the 3-dimensional topological insulators, the
vacuum of the Standard Model in its massive (gapped) phase and vacua of quantum
chromodynamics (QCD) with lattice fermions. The main property of the 3D systems
of this class is that the non-trivial topology leads to topologically protected gapless
fermionic states on the surface of a system or at the interface between topologically
different vacua. In case of 3He-B, these surface fermions have the Majorana nature.
Majorana fermions are still elusive in high-energy physics (originally the Majorana
nature was suggested for neutrino, but the proof is still missing). They do certainly exist on the surface of 3He-B, but their experimental detection is the challenge.
Superfluid 3He unite the modern directions in physics, and this allow us to consider
many problems in elementary particle physics, topological matter and cosmology from
a more general perspective using the experience from the many years investigations of
superfluid 3He. That is why superfluid 3He remains a priority in science as well in the
multi-disciplinary activity of the Low Temperature Laboratory.
Following this plan the broad collaboration continues between superfluid 3He community and the communities of high-energy physics, cosmology, cold gases, hightemperature superconductivity, topological insulators and semimetals, graphene, etc.
Annual Report 2014
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ACHIEVEMENTS IN 2014
High energy physics and gravity
In collaboration with Dr. Zubkov we studied Higgs bosons in particle physics and
condensed matter69,70. In condensed matter Higgs bosons - the amplitude modes - have
been experimentally investigated for many years. An example is superfluid 3He-B,
where the spontaneously broken symmetry leads to 4 Goldstone modes and at least 14
Higgs amplitude modes, which are characterized by angular momentum quantum
number J and parity. Zeeman splitting of Higgs modes with J=2+ and J=2- in magnetic
field has been observed already in 80's. Based on the relation E2(J+) + E2(J-) = 4Δ2
for the energy spectrum of these modes, the Nobel Prize winner Yoichiro Nambu proposed the general rule, which relates masses of Higgs bosons and masses of fermions.
Assuming that this rule is applicable to Standard Model, we suggested that the observed Higgs boson with mass 125 GeV may have a Nambu partner - the second Higgs
boson with mass 325 GeV. Together they satisfy the Nambu relation M12 + M22 = 4
M2(top), where M(top) is the top quark mass. A certain excess of events at 325 GeV
has been reported in 2011, and in early 2012, though not approved in the later 2012
experiments. The more detailed analysis of these events is required.
We also considered the scenario, in which the light Higgs scalar boson appears as the
pseudo-Goldstone boson. We discussed examples both in condensed matter and in relativistic field theory. In 3He-B one of the four 4 Nambu-Goldstone modes becomes the
Higgs boson: the small mass appears due to the weak spin-orbit interaction, which
explicitly violates the SU(2) symmetry of spin rotations. In this scenario the symmetry
breaking energy scale Δ is much higher than the Higgs mass scale. This light Higgs is
reperesented by the spin-wave mode measured in experiments with the longitudinal
NMR, and the Higgs mass corresponds to the Leggett frequency. Generation of the
light-Higgs mode by parametric instability of magnons BEC has been observed in the
ROTA cryostat71. A similar light-Higgs mechanism may explain why the mass 125
GeV of the observed Higgs boson is rather small compared to the electroweak scale at
which the Standard Model symmetry is spontaneously broken70.
In relation to dynamical Casimir effect and Unruh effect we considered the mirror
moving in the quantum vacuum72. We found the relation of this problem to the general
problem of polaron - the electron moving in the vacuum of the quantum field of phonons. We introduced the field-theoretical model of such a mirror, which contains the
multi-component spinor field interacting with the scalar field. We discussed the logarithmic divergence in the mirror mass and its relation to the general problem of the divergences in the energy of vacuum energy.
69
Volovik, G.E., and Zubkov, M.A., Higgs bosons in particle physics and in condensed matter, J. Low
Temp. Phys. 175, 486-497 (2014).
70
Volovik, G.E., and Zubkov, M.A., Scalar excitation with Leggett frequency in 3He-B and the 125 GeV
Higgs particle in top quark condensation models as Pseudo - Goldstone bosons, [arXiv:1410.7097].
71
Zavjalov, V.V., Autti, S., Eltsov, V.B., Heikkinen, P., and Volovik, G.E., Light Higgs channel of the
resonant decay of magnon BEC in superfluid 3He-B, [arXiv:1411.3983].
72
Volovik, G.E., and Zubkov, M.A., Mirror as polaron with internal degrees of freedom, Phys. Rev. D
90, 087702 (2014).
Annual Report 2014
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Topological media: superfluid 3He, quantum vacuum, graphene
Discovery of topological insulators, graphene and Dirac semimetals gave new impulse
to investigation of topological media, which started after discovery of topological
phases of superfluid 3He in seventies. Many quantum condensed matter systems are
strongly correlated and strongly interacting fermionic systems, which cannot be treated
perturbatively. However, topology allows us to determine generic features of their
fermionic spectrum, which are robust to perturbation and interaction. Topological matter is characterized by a nontrivial topology in momentum space.
The nontrivial momentum-space topology of graphene gives us the opportunity to
study many different properties of quantum vacua. In particular, we studied the effective gravity emerging in the vicinity of the Dirac poins. In graphene, in the presence of
strain the elasticity theory metric naturally appears. However, the fermionic quasiparticles experience different geometry. Fermions propagate in curved space, whose
metric is defined by expansion of the effective Hamiltonian near the topologically protected Fermi point. We discussed relation between both types of metric fields73. We
extended our consideration to the case, when the dislocations are present. We considered the situation, when the deformation is described by elasticity theory and calculated both torsion and emergent magnetic field carried by the dislocation. The dislocation
in addition to the quantized flux of emergent magnetic field carries also the singular
torsion, as physical part of emergent gravity. Torsion may be observed similar to the
Aharonov/Bohm effect in the scattering of fermiomic quasiparticles on the dislocation.
On the other hand, the multilayered graphene represents the system where the quantum
theory of gravity with anisotropic scaling is realized74. The anisotropic scaling, as it
was conjectured by Horava, makes the quantum gravity the ultraviolet complete, while
the conventional Einstein gravity experiences quadratic divergences when quantized.
In the vacua with the anisotropic scaling, the space and time are not equivalent, and
moreover they obey different scaling laws.
Both the superfluid 3He-A and graphene have topologically protected point nodes in
the fermionic spectrum. They both serve as examples of emerging relativistic quantum
field theory in 3+1 and 2+1 dimensions, respectively. In both systems the collective
modes and deformations provide the effective gauge and gravity fields acting on the
fermions. The perspective direction of investigations is to combine the physics of graphene and physics of superfluid phases of 3He as topological materials, whose quasiparticles behave as Majorana Weyl and Dirac fermions. We formulated the road map
of investigations75, which will allow us to use graphene for study the properties of superfluid 3He, to use superfluid 3He for study the properties of graphene, and to use
their combination to study the physics of topological quantum vacuum. In particular
we suggest experiments with superfluid 3He using graphene as an atomically thin
membrane impenetrable for 3He atoms but allowing for momentum and energy transfer.
73
Volovik, G.E., and Zubkov, M.A., Emergent geometry experienced by fermions in graphene in the
presence of dislocations, [arXiv:1412.2683].
74
Volovik, G.E., and Zubkov, M.A., Emergent Horava gravity in graphene, Ann. Phys. 340, 352-368
(2014).
75
Katsnelson, M.I., and Volovik, G.E., Topological matter: graphene and superfluid 3He, J. Low Temp.
Phys. 175, 655-666 (2014).
Annual Report 2014
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It is important to study the other possible phases of superfluid 3He, which emerge in
aerogel, or thin films of liquid 3He between the graphene sheets. In particular there can
be the polar phase with nodal lines and planar phase with Dirac points. The time reversal symmetric planar phase is of special interest both for topological insulators and for
Standard Model. We provided topological classification of states with the symmetry of
the planar phase76. Compared to the B-phase (class DIII in classification of Altland
and Zirnbauer), it has an additional symmetry, which modifies the topology. We analyze the topology in terms of explicit mappings from the momentum space, and also
discuss explicitly the mapping between topological invariants for the 3+1 B-phase and
2+1 planar phase. Due to this mapping the bulk-boundary correspondence for the 3D
B-phase can be inferred from that for the 2D planar phase.
The momentum-space topology is also instrumental for the resolution of the paradox
of the angular momentum in chiral superfluids and superconductors such as 3He-A77.
The magnitude of the angular momentum is determined by the spectral flow through
the gapless fermionic states, which live either in bulk liquid, or within the vortex cores
or on the boundaries of the system. It is the condensed-matter realization of the chiral
anomaly in particle physics.
Majorana fermions in 3He and particle physics
Majorana fermions could serve as the building blocks for the construction of elementary particles. In condensed matter the Majorana particles are realized as Andreev
bound states with zero energy on surfaces, interfaces, and vortices in different phases
of the p-wave superfluids. We considered Andreev–Majorana (AM) modes in the chiral superfluid 3He-A and time reversal invariant phases: superfluid 3He-B, planar and
polar phases78. The AM zero modes are determined by topology in the bulk and disappear at the quantum phase transition from the topological to non-topological state of
the superfluid. The topology of AM modes demonstrates the interplay of dimensions.
In particular, the zero-dimensional Weyl points in chiral superfluids (the Berry phase
monopoles in momentum space) give rise to the one-dimensional Fermi arc of AM
bound states on the surface and to the one-dimensional flat band of AM modes in the
vortex core. The one-dimensional nodal line in the polar phase produces a twodimensional flat band of AM modes on the surface. The interplay of dimensions also
connects the AM states in superfluids with different dimensions. For example, the topological properties of the spectrum of bound states in three-dimensional 3He-B are
connected to the properties of the spectrum in the two-dimensional planar phase (thin
film).
In relation to particle physics we considered the system of the multi-component Majorana spinors79. In the presence of the discrete symmetry the system in the vicinity of
76
Makhlin, Yu., Silaev, M., and Volovik, G.E., Topology of the planar phase of superfluid 3He and bulk
boundary correspondence for three-dimensional topological superconductors, Phys. Rev. B 89, 174502
(2014).
77
Volovik, G.E., Orbital momentum of chiral superfluids and spectral asymmetry of edge states, Pis’ma
ZhETF 100, 843-846 (2014).
78
Silaev, M.A., and Volovik, G.E., Andreev-Majorana bound states in superfluids, JETP 119, 10421057 (2014).
79
Volovik, G.E., and Zubkov, M.A., Emergent Weyl spinors in multi-fermion systems, Nucl. Phys. B
881, 514-538 (2014).
Annual Report 2014
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the topologically stable Fermi point is reduced to the 4-component real spinor, which
can be represented as Weyl fermion with 2 complex components. Those fermions experience the emergent gauge field and the gravitational field given by the emergent
veirbein. Both these fields (the emergent gauge field and the emergent gravitational
field) originate from certain collective excitations of the original system. This construction may solve the puzzle, why the Schrödinger equation contains complex numbers, while all physical quantities are real. It demonstrates that the complex numbers
may originate from the real numbers describing the Majorana fermions. The original
system of the multi-component Majorana fermions is naturally described in terms of
real numbers only. In the vicinity of the topologically protected Fermi point this system is reduced to the effective low energy theory with Weyl fermions. At the electroweak transition the 4 real components of left Weyl fermions combine with that of right
fermions to form 8 real components of massive Dirac fermions. At low energy the Dirac equation transforms to the Schrödinger equation. The imaginary unit i in the
Schrödinger equation originates from the 4x4 real matrix I, which commutes with the
original real Hamiltonian and which obeys the equation I2=-180. This shows, that the
appearance of complex numbers in quantum mechanics may be the emergent phenomenon, i.e. complex numbers may appear in the low energy description of the underlying high-energy system, whose quantum mechanics is described by real numbers.
Flat band and route to room-temperature superconductivity
The flat bands were first discussed in relation to the Landau levels in magnetic field.
However, they may emerge even without any magnetic field. Examples are: strongly
interacting systems in condensed matter, which form the so called fermionic condensate; 2+1 dimensional quantum field theory, which is dual to a gravitational theory in
the anti-de Sitter background; layered systems with integer-valued pseudo-spin; the
surface of the topological media with nodal lines in bulk; fermion modes on topological objects in topological materials etc.68. The flat band has an extremely singular density of states, which gives the linear dependence of the critical temperature of superconducting transition on the coupling in the Cooper channel, in contrast to the exponential suppression of transition temperature in the conventional superconductors.
Thus the flat band may give rise to superconductivity with high transition temperature.
This may open the route to room-temperature superconductivity. Using the flat band
phenomenon, we proposed81 an explanation for some evidences of high-T superconductivity at the interfaces of graphite. A network of line defects with flat bands appears at the interfaces between two slightly twisted graphite structures. Due to the flat
band the probability to find high temperature superconductivity at these quasi onedimensional corridors is strongly enhanced. When the network of superconducting
lines is dense it becomes effectively two-dimensional. The model provides an explanation for several reports on the observation of superconductivity up to room temperature
in the highly oriented graphite samples.
The goal of further investigations should be the search for (or artificial fabrication of)
the layered and/or twinned systems, which have the flat band appropriate for achievement of superconductivity with high transition temperature.
80
Volovik, G.E., and Zubkov, M.A., Emergent Weyl fermions and the origin of i=\sqrt{-1} in quantum
mechanics, JETP Lett. 99, 481-486 (2014).
81
Esquinazi, P., Heikkilä, T.T., Lysogorskiy, Yu.V., Tayurskii, D.A., and Volovik, G.E., On the superconductivity of graphite interfaces, JETP Lett. 100, 336-339 (2014).
Annual Report 2014
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BRAIN RESEARCH UNIT
The research programs of the Brain Research Unit (BRU) have continued to deepen
the understanding of human brain function in health and disease. Specifically, we have
been exploiting, developing, and integrating advanced spatiotemporal methods of noninvasive human neuroimaging using magnetoencephalography (MEG), functional
magnetic resonance imaging (fMRI), and transcranial magnetic stimulation (TMS).
The research has continued to include design and construction of stimulation and monitoring devices to create versatile but controlled stimulus environments for experiments in systems neuroscience.
In 2014, Brain Research Unit comprised research groups of Attention and Memory
(led by Prof. Synnöve Carlson), CliniMEG (led by Doc. Nina Forss), Human Systems
Neuroscience (led by Academician Riitta Hari; including instrumentation development
group led by Doc. Veikko Jousmäki), Multimodal Neuroimaging, Signal Analysis, and
Modeling (led by Prof. Matti Hämäläinen), Imaging Language (led by Acad. Prof.
Riitta Salmelin), and Visual Cognition and Awareness (led by Doc. Juha Silvanto).
Our main method is MEG, the noninvasive time-resolved method to study human
brain function by measuring the brain’s weak magnetic fields. MEG method allows
monitoring of brain dynamics totally non-invasively in healthy and diseased humans
during different tasks and conditions. Our 306-channel neuromagnetometer (Elekta
Neuromag, Elekta Oy), functional since 1998 and upgraded in 2008, houses 204 gradiometers and 102 magnetometers with whole-scalp coverage.
We also use extensively fMRI at the Advanced Magnetic Imaging (AMI) Centre of the
Aalto University; fMRI with its excellent spatial resolution complements the superb
temporal resolution of MEG in tracking activation patterns and sequences in the human brain. The AMI Centre operates a 3-tesla MRI/fMRI superconducting magnet
since 2002, and the scanner was renewed in 2011 (Siemens MAGNETOM Skyra).
At the Aalto TMS laboratory, fully operational since the beginning of 2013, we investigate causal relations between brain areas and behavior. Aalto TMS has two neuronavigated TMS systems (BiStim2 & Rapid2, Company Ltd), as well as an EEG recording system (NeurOne) that can be used together with the TMS.
The MEG Core, the AMI Centre (technical director Toni Auranen), and Aalto TMS
(scientific director Synnöve Carlson) comprise since 2013 the Aalto NeuroImaging
(ANI) research infrastructure (http://ani.aalto.fi) directed by Doc. Veikko Jousmäki
and administered by OVLL. The annual ANI report is available at the ANI website.
ANI is one of the large infrastructures of Aalto University School of Science. Together
with the Biomag Laboratory at HUCH, ANI has formed the NEUROIMAGING infrastructure that has a separate steering board chaired by Aalto-SCI School’s Dean.
The ANI infrastructure is included on the Academy of Finland’s roadmap for research
infrastructures for 2014–2020, as a major component of the wider Helsinki-area
NEUROIMAGING research infrastructure, and of the national-level consortium Finnish Infrastructures for Functional Imaging (FIFI; Riitta Salmelin as Chair of Coordinating Group).
BRU and our brain imaging infrastructures were visited in 2014 by a team of US scientists during their Europe–Asia tour, organized by the World Technology Evaluation
Center and sponsored by the National Science Foundation, aiming for “Global Assessment of Research in Neuroimaging”; ours was the only neuroimaging infrastrucAnnual Report 2014
– 65 –
ture visited in Finland. They concluded that Aalto University is “one of the leaders in
understanding
the
human
brain”.
For
the
final
report,
see
http://www.wtec.org/neuralimaging/docs/Neuroimaging-FinalReport-Web.pdf.
In September 2014, Dr. Matti Hämäläinen from MGH/Harvard started as our new full
professor of Systems neuroscience. Juha Silvanto (University of Westminster, London,
UK) continued to have part of his vision-research team at BRU.
Aalto Brain Centre (ABC), a multidisciplinary thematic center receiving strategic
funding for neuroscience and neurotechnology from the Aalto School of Science started in rather full speed in June 2014; Riitta Hari had been responsible for the ramp-up
period and Matti Hämäläinen was appointed as the Director of the ABC. In 2014, the
ABC activities included 4 (in fall) invited lectures by prominent international neuroscientists and contribution to 3 symposia. ABC also started a biweekly seminar series.
In fall 2014, the local faculty has given lectures to familiarize the ABC community
with ongoing neuroscience research at Aalto.
Three BRU scientists belong to the executive board of the BRAHE initiative (Brain
Research at Aalto University and University of Helsinki; Synnöve Carlson as chair of
the executive board, Nina Forss and Riitta Salmelin). Since October 2012, four
BRAHE postdocs work in close contact with Aalto; the two Aalto-based BRAHE
postdocs have been supported by the Aalto SCI strategic funding for neuroscience and
neurotechnology. The 3rd scientific BRAHE meeting was organized in October 2014
to present and promote collaborative brain research between Aalto University and the
University of Helsinki. The meeting highlights included presentations describing the
research infrastructures of both Aalto University and University of Helsinki, talks
about recent progress in neuroscience research in the two universities, snapshots (2min highlights) by young researchers, a poster session, and a keynote lecture by Assistant Professor, Academy Research Fellow Petri Ala-Laurila (Aalto University and
University of Helsinki).
BRU continued to participate in and lead aivoAALTO, the multidisciplinary research
project comprising all three schools of the Aalto University; aivoAALTO was directed
by Riitta Hari and coordinated by Doc. Elina Pihko; the project officially ended in
2014.
In 2014, BRU organized 3 international Elekta Neuromag Triux introductory MEG
courses, each lasting for 5 days and including both lectures and hands-on data acquisition and analysis sessions, and one Elekta Neuromag service training. The courses
were carried out in collaboration with Elekta Oy. The majority of the participants came
from abroad (Toronto, Canada; Gurgaon, India; Philadelphia, USA), mainly from new
MEG installation sites of Elekta Oy.
BRU, together with ANI, AMI Centre, Aalto TMS, ABC, and the Doctoral Program
Brain & Mind of the Aalto University and University of Helsinki, organized in October 2014 a one-day TMS workshop directed by Synnöve Carlson. The workshop included lectures by Eva Feredoes (University of Reading, UK), John Evans (Cardiff
University, UK), Risto Ilmoniemi (Aalto University) and Christian Ruff (University of
Zurich, Switzerland), and a visit to Aalto TMS Laboratory. The workshop had about
60 attendees. In autumn 2014, BRU together with the department of Biomedical Engineering and Computational Science (BECS) organized a lecture series “Aivoaakkoset”
(the ABC of the brain) that included 12 lectures on modern brain research and a panel
discussion. The lectures were open to all students and personnel of Aalto University.
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In March 2014, aivoAALTO organized—for the fifth time in connection with the annual international Brain Awareness Week—a thematic afternoon for the broad public
on a topic ‘Voiko aivotutkija lukea mieltäsi?’ (‘Can a brain researcher read your
mind?’) This event had about 80 attendees.
BRU maintains a technical research contract with Elekta Oy.
BRU continued to participate actively (Nina Forss, Riitta Hari, and Riitta Salmelin as
research leaders) in the Salwe SHOK Research Program that aims to prevent and treat
socioeconomically important diseases; the program was financed by TEKES and it
ended in 2014. Our clinically important results continue to be translated to clinical environment also via the CliniMEG team.
The senior scientists have given several national and international lectures and participated in peer-reviewing of scientific publications, research grants, foreign research
programs, and have given statements for the appointment of professors in universities
abroad.
Below we list our scientific achievements from 2014 in the form of published papers,
with abstracts from the original papers. The total number of peer-reviewer publications
in international journals was 53.
At the end of 2014, Aalto School of Science informed about large organizational
changes that affect BRU as well. Consequently, starting from 1 Jan 2015, together
with BECS (Department of Biomedical Engineering and Computational Science), we
will form a new Department of Neuroscience and Biomedical Engineering, and we are
in the process of planning a move of the offices and MEG Core to Otakaari 3.
Annual Report 2014
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ATTENTION AND MEMORY
Person years: 1 professor, 1 postdoc, 4 PhD students
1. Anurova I, Renier LA, De Volder AG, Carlson S, Rauschecker JP: Relationship
between cortical thickness and functional activation in the early blind. Cerebral
Cortex 2014, Feb 10. [Epub ahead of print].
Early blindness results in both structural and functional changes of the brain. However,
these changes have rarely been studied in relation to each other. We measured alterations in cortical thickness (CT) caused by early visual deprivation and their relationship with cortical activity. Structural and functional magnetic resonance imaging was
performed in 12 early blind (EB) humans and 12 sighted controls (SC). Experimental
conditions included one-back tasks for auditory localization and pitch identification,
and a simple sound-detection task. Structural and functional data were analyzed in a
whole-brain approach and within anatomically defined regions of interest in sensory
areas of the spared (auditory) and deprived (visual) modalities. Functional activation
during sound-localization or pitch-identification tasks correlated negatively with CT in
occipital areas of EB (calcarine sulcus, lingual gyrus, superior and middle occipital
gyri, and cuneus) and in nonprimary auditory areas of SC. These results suggest a link
between CT and activation and demonstrate that the relationship between cortical
structure and function may depend on early sensory experience, probably via selective
pruning of exuberant connections. Activity-dependent effects of early sensory deprivation and long-term practice are superimposed on normal maturation and aging. Together these processes shape the relationship between brain structure and function over
the lifespan.
2. Boldt R, Gogulski J, Guzman-Lopez J, Carlson S, Pertovaara A: Two-point tactile
discrimination ability is influenced by temporal features of stimulation. Experimental Brain Research 2014, 232: 2179–2185.
Two-point discrimination threshold is commonly used for assessing tactile spatial
resolution. Since the effect of temporal features of cutaneous test stimulation on spatial
discrimination ability is not yet well known, we determined whether the ability to discriminate between two stimulus locations varies with the interstimulus interval (ISI) of
sequentially presented tactile stimuli or the length of the stimulus train. Electrotactile
stimuli were applied to one or two locations on the skin of the thenar eminence of the
hand in healthy human subjects. Tactile discrimination ability was determined using
methods based on the signal detection theory allowing the assessment of sensory performance, independent of the subject's response criterion. With stimulus pairs, the
ability to discriminate spatial features of stimulation (one location vs. two stimulus
locations 4 cm apart) was improved when the ISI was equal to or longer than that required for tactile temporal discrimination. With stimulus trains, the ability to discriminate spatial features of stimulation was significantly improved with an increase in the
stimulus train (from 3 to 11 pulses corresponding to train lengths from 40 to 200 ms).
These results indicate that temporal features of tactile stimulation significantly influence sensory performance in a tactile spatial discrimination task. Precise control of
temporal stimulus parameters should help to reduce variations in results on the twopoint discrimination threshold.
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3. Boldt R, Seppä M, Malinen S, Tikka P, Hari R, Carlson S: Spatial variability of
functional brain networks in early-blind and sighted subjects. NeuroImage 2014,
95: 208–216. [in collaboration with Systems Neuroscience group]
To further the understanding how the human brain adapts to early-onset blindness, we
searched in early-blind and normally-sighted subjects for functional brain networks
showing the most and least spatial variabilities across subjects. We hypothesized that
the functional networks compensating for early-onset blindness undergo cortical reorganization. To determine whether reorganization of functional networks affects spatial
variability, we used functional magnetic resonance imaging to compare brain networks, derived by independent component analysis, of 7 early-blind and 7 sighted subjects while they rested or listened to an audio drama. In both conditions, the blind
compared with sighted subjects showed more spatial variability in a bilateral parietal
network (comprising the inferior parietal and angular gyri and precuneus) and in a bilateral auditory network (comprising the superior temporal gyri). In contrast, a visionrelated left-hemisphere-lateralized occipital network (comprising the superior, middle
and inferior occipital gyri, fusiform and lingual gyri, and the calcarine sulcus) was less
variable in blind than sighted subjects. Another visual network and a tactile network
were spatially more variable in the blind than sighted subjects in one condition. We
contemplate whether our results on inter-subject spatial variability of brain networks
are related to experience-dependent brain plasticity, and we suggest that auditory and
parietal networks undergo a stronger experience-dependent reorganization in the earlyblind than sighted subjects while the opposite is true for the vision-related occipital
network.
4. Gogulski J, Boldt R, Savolainen P, Guzmán-López J, Carlson S, Pertovaara A: A
segregated neural pathway for prefrontal top-down control of tactile discrimination. Cerebral Cortex 2015, 25: 161–166.
It has proven difficult to separate functional areas in the prefrontal cortex (PFC), an
area implicated in attention, memory, and distraction handling. Here, we assessed in
healthy human subjects whether PFC subareas have different roles in top-down regulation of sensory functions by determining how the neural links between the PFC and the
primary somatosensory cortex (S1) modulate tactile perceptions. Anatomical connections between the S1 representation area of the cutaneous test site and the PFC were
determined using probabilistic tractography. Single-pulse navigated transcranial magnetic stimulation of the middle frontal gyrus-S1 link, but not that of the superior
frontal gyrus-S1 link, impaired the ability to discriminate between single and twin tactile pulses. The impairment occurred within a restricted time window and skin area.
The spatially and temporally organized top-down control of tactile discrimination
through a segregated PFC-S1 pathway suggests functional specialization of PFC subareas in fine-tuned regulation of information processing.
5. Hayashi MJ, Kantele M, Walsh V, Carlson S, Kanai R: Dissociable neuroanatomical correlates of subsecond and suprasecond time perception. Journal of Cognitive
Neuroscience 2014, 26: 1685–1693.
The ability to estimate durations varies across individuals. Although previous studies
have reported that individual differences in perceptual skills and cognitive capacities
Annual Report 2014
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are reflected in brain structures, it remains unknown whether timing abilities are also
reflected in the brain anatomy. Here, we show that individual differences in the ability
to estimate subsecond and suprasecond durations correlate with gray matter (GM) volume in different parts of cortical and subcortical areas. Better ability to discriminate
subsecond durations was associated with a larger GM volume in the bilateral anterior
cerebellum, whereas better performance in estimating the suprasecond range was associated with a smaller GM volume in the inferior parietal lobule. These results indicate
that regional GM volume is predictive of an individual's timing abilities. These morphological results support the notion that subsecond durations are processed in the motor system, whereas suprasecond durations are processed in the parietal cortex by utilizing the capacity of attention and working memory to keep track of time.
6. Okamoto Y, Kitada R, Tanabe HC, Hayashi MJ, Kochiyama T, Munesue T,
Ishitobi M, Saito DN, Yanaka HT, Omori M, Wada Y, Okazawa H, Sasaki AT,
Morita T, Itakura S, Kosaka H, Sadato N: Attenuation of the contingency detection
effect in the extrastriate body area in autism spectrum disorder. Neuroscience Research 2014, 87: 66–76.
Detection of the contingency between one's own behavior and consequent social
events is important for normal social development, and impaired contingency detection may be a cause of autism spectrum disorder (ASD). To depict the neural underpinnings of this contingency effect, 19 adults with ASD and 22 control participants
underwent functional MRI while imitating another's actions and their actions being
imitated by the other. As the extrastriate body area (EBA) receives efference copies of
one's own movements, we predicted that the EBA would show an atypical response
during contingency detection in ASD. We manipulated two factors: the congruency of
the executed and observed actions, and the order of action execution and observation.
Both groups showed the congruency effect in the bilateral EBA during imitation.
When action preceded observation, the left EBA of the control group showed the congruency effect, representing the response to being imitated, indicating contingency detection. The ASD group showed a reduced contingency effect in the left EBA. These
results indicate that the function of the EBA in the contingency detection is altered in
ASD.
7. Jiang P, Tokariev M, Aronen ET, Salonen O, Ma Y, Vuontela V, Carlson S: Responsiveness and functional connectivity of the scene-sensitive retrosplenial complex in 7-11-year-old children. Brain and Cognition 2014, 92C: 61–72.
Brain imaging studies have identified two cortical areas, the parahippocampal place
area (PPA) and the retrosplenial complex (RSC), that respond preferentially to the
viewing of scenes. Contrary to the PPA, little is known about the functional maturation
and cognitive control of the RSC. Here we used functional magnetic resonance imaging and tasks that required attention to scene (or face) images and suppression of face
(or scene) images, respectively, to investigate task-dependent modulation of activity in
the RSC and whole-brain functional connectivity (FC) of this area in 7-11-year-old
children and young adults. We compared responsiveness of the RSC with that of the
PPA. The RSC was selectively activated by scene images in both groups, albeit less
than the PPA. Children modulated activity between the tasks similarly in the RSC and
PPA, and to the same extent as adults in PPA, whereas adults modulated activity in the
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RSC less than in PPA. In children, the whole brain FC of the RSC was stronger in the
Sf than Fs task between the left RSC and right fusiform gyrus. The between groups
comparison suggested stronger FC in children than adults in the Sf task between the
right RSC and the left inferior parietal lobule and intraparietal sulcus. Together the results suggest that the function of the RSC and the related networks undergo dynamic
changes over the development from 7-11-year-old children to adulthood.
8. Carlson S: Miten muisti on selitettävissä? Duodecim 2014, 130: 2431-2434.
Jouluna luodaan muistoja ja muistellaan menneitä. Muistiin osallistuvat hermoverkot
ovat täydessä iskussa. Tässä kirjoituksessa pohditaan muistin monimuotoisuutta sekä
muistamisen ja unohtamisen keveyttä ja kerrotaan, miten neurotiede selittää muistin
toimintaa. Muisti rakentuu hermosolujen välisten yhteyksien, synapsien, toimintaan,
jota geenit ohjaavat ja kokemukset muovaavat.
Doctoral thesis
Robert Boldt (December 11, 2014)
Functional and anatomical brain networks - Brain networks during naturalistic auditory stimuli, tactile stimuli and rest. Functional network plasticity in early-blind subjects.
(Supervisor Prof. Synnöve Carlson, Opponent Prof. Tianzi Jiang)
Hearing is a versatile sense allowing us, among other things, to avoid danger and engage in pleasurable discussions. The ease with which we follow a conversation in a
noisy environment is astonishing. Study I in this thesis used functional magnetic resonance imaging to explore the large-scale organization of speech and non-speech sound
processing during a naturalistic stimulus comprised of an audio drama. Two largescale functional networks processed the sounds. Hearing is essential for blind subjects.
Anatomical and functional changes in the brains of blind people allow them to experience a detailed auditory world, compensating for the lack of vision. Therefore, comparing early-blind subjects brains to those of sighted people during naturalistic stimuli
reveals fundamental differences in brain organization.
In Study II, naturalistic stimuli were employed to explore whether one of the most distinguishing traits of the auditory system the left-lateralized responses to speech changes following blindness. As expected, in sighted subjects, speech processing was lefthemisphere dominant. Curiously, the left-hemisphere dominance for speech was absent or even reversed in blind subjects. In early-blind people, the senses beyond vision
are strained as they try to compensate for the loss of sight; on the other hand, the occipital cortices are devoid of normal visual information flow. Interestingly, in blind
people, senses other than vision recruit the occipital cortex. Additional to changes in
the occipital cortex, the sensory cortices devoted to touch and hearing change. Data
presented here suggested more inter-subject variability in auditory and parietal areas in
blind subjects compared with sighted subjects. The study suggested that the greater the
inter-subject variability of the network, the greater the experience-dependent plasticity
of that network. As the prefrontal areas display large inter-subject spatial variability,
the activation of the prefrontal cortex varies greatly. The variable activation might
partly explain why the top-down influences of the prefrontal cortex on tactile discrimination are not well understood. In the fourth study, anatomical variability was assessed
on an individual level, and transcranial magnetic stimulation was targeted at individuAnnual Report 2014
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ally-chosen prefrontal locations indicated in tactile processing. Stimulation of one out
of two prefrontal cortex locations impaired the subjects ability to distinguish a single
tactile pulse from paired pulses. Thus, the study suggested that tactile information is
regulated by functionally specialized prefrontal subareas.
CliniMEG
Person years: 0.5 docents, 3 PhD students
1. Forss N, Vartiainen N: Krooniseen kipuun liittyvien aivomuutosten kuvantaminen.
Duodecim 2014, 130: 1507–1514
Akuutti kipu on ihmisen selviytymisen kannalta välttämätön varoitussignaali, mutta
kroonistuessaan kipu menettää alkuperäisen hyödyllisen tarkoituksensa ja aiheuttaa
tarpeetonta kärsimystä ja mittavia kansantaloudellisia menetyksiä. Modernit aivokuvantamismenetelmät ovat mahdollistaneet kipuun liittyvien toiminnallisten ja rakenteellisten aivomuutosten objektiivisen havainnoinnin. Viimeaikaisten tutkimusten mukaan krooniseen kipuun ei liity pelkästään akuuttia kipua käsittelevien alueitten poikkeavan voimakasta tai pitkittynyttä toimintaa vaan kullekin kiputilalle tyypillisten aivoverkostojen aktivoitumista, aivokuoren muovautumismuutoksia sekä harmaan aineen paikallista vähentymistä useilla aivoalueilla. Krooniseen kipuun liittyvien aivomuutosten avulla voidaan paremmin ymmärtää erilaisten kroonisten kiputilojen mekanismeja, mikä on edellytys kroonisten kiputilojen diagnostiikalle sekä tehokkaiden
hoito- ja kuntoutusmenetelmien kehittämiselle.
2. Kirveskari E, Vartiainen NV, Kallio-Laine K, Kalso E, Forss N: Normal laserevoked cortical responses in patients with chronic hemibody pain. European Journal of Pain 2014.
Background: Patients with widespread unilateral chronic pain associated with recurrent herpes simplex virus (HSV) infections show functional and/or structural changes
in the insula, anterior cingulate cortex, frontal and prefrontal cortices, as well as the
thalamus, suggesting central dysfunction of the pain system in these patients. Central
pain has been associated with attenuated laser-evoked cortical responses. We aimed to
clarify whether the observed deficient activation of these areas to acute nociceptive
stimuli is due to a lesion at a lower level of pain processing pathways.
Methods: We explored the functional integrity of the ascending nociceptive pathways
by recording the cortical-evoked responses to noxious laser stimulation using magnetoencephalography and electroencephalography in eight patients (age 41–51  years,
mean 46) with recurrent HSV infections and a history of chronic, spontaneous, widespread unilateral pain, and in nine age-matched healthy control subjects.
Results: The cortical-evoked fields of the HSV patients originating from the secondary
somatosensory and posterior parietal cortices, as well as the evoked potentials recorded from the midline, did not differ from those of the control subjects, indicating functionally intact ascending nociceptive pathways.
Conclusions: The present results show that our patients with chronic hemibody pain do
not show signs of spinothalamic tract lesion. This indicates normal processing of sensory aspects of painful stimuli, while higher pain processing areas show altered activation. We conclude that normal laser-evoked magnetic fields (LEF) or laser-evoked potentials (LEP) may not exclude central pain condition.
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HUMAN SYSTEMS NEUROSCIENCE
Person years: 1 professor, 2 docents (with ANI and aivoAALTO administrative
dueties), 6 postdoc, 4 PhD students
1. Clumeck C, Sarah Suarez Garcia S, Bourguignon M, Wens V, Op de Beeck M,
Marty B, Deconinck N, Soncarrieu M-V, Goldman S, Jousmäki V, Van Bogaert P,
De Tiège X: Preserved coupling between the reader’s voice and the listener’s cortical activity in autism spectrum disorders. PLoS One 2014, 9: e92329.
PURPOSE: Investigating the steadiness of the phase-coupling between the time-course
of the reader's voice and brain signals of subjects with autism spectrum disorder
(ASD) passively listening to connected speech using magnetoencephalography
(MEG). In typically developed subjects, such coupling occurs at the right posterior
temporal sulcus (pSTS) for frequencies below 1 Hz, and reflects the neural processing
of sentence-level rhythmic prosody at the prelexical level. METHODS: Cortical neuromagnetic signals were recorded with MEG (Elekta Oy, Finland) while seven righthanded and native French-speaking ASD subjects (six males, one female, range: 13-20
years) listened to live (Live) or recorded (Recorded) voices continuously reading a text
in French for five minutes. Coherence was computed between the reader's voice timecourse and ASD subjects' MEG signals. Coherent neural sources were subsequently
reconstructed using a beamformer. KEY FINDINGS: Significant coupling was found
at 0.5 Hz in all ASD subjects in Live and in six subjects in Recorded. Coherent sources
were located close to the right pSTS in both conditions. No significant difference was
found in coherence levels between Live and Recorded, and between ASD subjects and
ten typically developed subjects (right-handed, native French-speaking adults, 5 males,
5 females, age range: 21-38 years) included in a previous study. SIGNIFICANCE:
This study discloses a preserved coupling between the reader's voice and ASD subjects' cortical activity at the right pSTS. These findings support the existence of preserved neural processing of sentence-level rhythmic prosody in ASD. The preservation
of early cortical processing of prosodic elements in verbal language might be exploited
in therapeutic interventions in ASD.
2. Hari R, Bourguignon M, Piitulainen H, Smeds E, De Tiège X, Jousmäki V: Human
primary motor cortex is both activated and stabilizes during observation of other
person’s phasic motor actions. Philosophical Transactions B 2014, 369: 20130171.
When your favourite athlete flops over the high-jump bar, you may twist your body in
front of the TV screen. Such automatic motor facilitation, 'mirroring' or even overt
imitation is not always appropriate. Here, we show, by monitoring motor-cortex brain
rhythms with magnetoencephalography (MEG) in healthy adults, that viewing intermittent hand actions of another person, in addition to activation, phasically stabilizes
the viewer's primary motor cortex, with the maximum of half a second after the onset
of the seen movement. Such a stabilization was evident as enhanced cortex-muscle
coherence at 16-20 Hz, despite signs of almost simultaneous suppression of rolandic
rhythms of approximately 7 and 15 Hz as a sign of activation of the sensorimotor cortex. These findings suggest that inhibition suppresses motor output during viewing another person's actions, thereby withholding unintentional imitation.
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3. Kauppi JP, Pajula J, Tohka J: A versatile software package for inter-subject correlation based analyses of fMRI. Frontiers in Neuroinformatics 2014, 8: 2 (13 pages).
In the inter-subject correlation (ISC) based analysis of the functional magnetic resonance imaging (fMRI) data, the extent of shared processing across subjects during the
experiment is determined by calculating correlation coefficients between the fMRI
time series of the subjects in the corresponding brain locations. This implies that ISC
can be used to analyze fMRI data without explicitly modeling the stimulus and thus
ISC is a potential method to analyze fMRI data acquired under complex naturalistic
stimuli. Despite of the suitability of ISC based approach to analyze complex fMRI data, no generic software tools have been made available for this purpose, limiting a
widespread use of ISC based analysis techniques among neuroimaging community. In
this paper, we present a graphical user interface (GUI) based software package, ISC
Toolbox, implemented in Matlab for computing various ISC based analyses. Many
advanced computations such as comparison of ISCs between different stimuli, time
window ISC, and inter-subject phase synchronization are supported by the toolbox.
The analyses are coupled with re-sampling based statistical inference. The ISC based
analyses are data and computation intensive and the ISC toolbox is equipped with
mechanisms to execute the parallel computations in a cluster environment automatically and with an automatic detection of the cluster environment in use. Currently, SGEbased (Oracle Grid Engine, Son of a Grid Engine, or Open Grid Scheduler) and Slurm
environments are supported. In this paper, we present a detailed account on the methods behind the ISC Toolbox, the implementation of the toolbox and demonstrate the
possible use of the toolbox by summarizing selected example applications. We also
report the computation time experiments both using a single desktop computer and two
grid environments demonstrating that parallelization effectively reduces the computing
time. The ISC Toolbox is available in https://code.google.com/p/isc-toolbox/
4. Kivistö K, Nevalainen P, Lauronen L, Tupola S, Pihko E, Kivitie-kallio S: Somatosensory and auditory processing in opioid-exposed newborns with neonatal abstinence syndrome: a magnetoencephalographic approach. Journal of MaternalFetal & Neonatal Medicine 2014, 11: 1–5.
Abstract Objective: Opioid exposure during pregnancy is a potential risk factor for the
developing central nervous system of the fetus. We studied evoked responses in buprenorphine-exposed newborns who displayed neonatal abstinence syndrome (NAS) to
elucidate the possible alterations in functioning of the somatosensory and auditory systems. Methods: We compared somatosensory (SEFs) and auditory evoked magnetic
fields (AEFs), recorded with magnetoencephalography (MEG), of 11 prenatally buprenorphine-exposed newborns with those of 12 healthy newborns. Peak latencies,
source strength and location of SEFs or AEFs were recorded. Results: AEFs were present in all buprenorphine-exposed newborns without significant differences from those
of healthy newborns. In contrast, though no group level differences in SEFs existed, at
individual level the response deviated from the typical neonatal morphology in four
buprenorphine-exposed newborns. Conclusions: Although buprenorphine exposure
during pregnancy does not seem to cause constant deficiencies in somatosensory or
auditory processing, in some newborns the typical development of somatosensory
networks may be - at least transiently - disrupted.
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5. Koskinen M, Seppä M: Uncovering cortical MEG responses to listened audiobook
stories. NeuroImage 2014, 100: 263–270.
Naturalistic stimuli, such as normal speech and narratives, are opening up intriguing
prospects in neuroscience, especially when merging neuroimaging with machine learning methodology. Here we propose a task-optimized spatial filtering strategy for uncovering individual magnetoencephalographic (MEG) responses to audiobook stories.
Ten subjects listened to 1-h-long recording once, as well as to 48 repetitions of a 1min-long speech passage. Employing response replicability as statistical validity and
utilizing unsupervised learning methods, we trained spatial filters that were able to
generalize over datasets of an individual. For this blind-signal-separation (BSS) task,
we derived a version of multi-set similarity-constrained canonical correlation analysis
(SimCCA) that theoretically provides maximal signal-to-noise ratio (SNR) in this setting. Irrespective of significant noise in unaveraged MEG traces, the method successfully uncovered feasible time courses up to ~120 Hz, with the most prominent signals
below 20 Hz. Individual trial-to-trial correlations of such time courses reached the level of 0.55 (median 0.33 in the group) at ~0.5 Hz, with considerable variation between
subjects. By this filtering, the SNR increased up to 20 times. In comparison, independent component analysis (ICA) or principal component analysis (PCA) did not improve
SNR notably. The validity of the extracted brain signals was further assessed by inspecting their associations with the stimulus, as well as by mapping the contributing
cortical signal sources. The results indicate that the proposed methodology effectively
reduces noise in MEG recordings to that extent that brain responses can be seen to
nonrecurring audiobook stories. The study paves the way for applications aiming at
accurately modeling the stimulus-response-relationship by tackling the response variability, as well as for real-time monitoring of brain signals of individuals in naturalistic
experimental conditions.
6. Lahnakoski JM, Glerean E, Jääskeläinen IP, Hyönä J, Hari R, Sams M, Nummenmaa L: Synchronous brain activity across individuals underlies shared psychological perspectives. NeuroImage 2014, 100C: 316–324.
For successful communication, we need to understand the external world consistently
with others. This task requires sufficiently similar cognitive schemas or psychological
perspectives that act as filters to guide the selection, interpretation and storage of sensory information, perceptual objects and events. Here we show that when individuals
adopt a similar psychological perspective during natural viewing, their brain activity
becomes synchronized in specific brain regions. We measured brain activity with functional magnetic resonance imaging (fMRI) from 33 healthy participants who viewed a
10-min movie twice, assuming once a 'social' (detective) and once a 'non-social' (interior decorator) perspective to the movie events. Pearson's correlation coefficient was
used to derive multisubject voxelwise similarity measures (inter-subject correlations;
ISCs) of functional MRI data. We used k-nearest-neighbor and support vector machine
classifiers as well as a Mantel test on the ISC matrices to reveal brain areas wherein
ISC predicted the participants' current perspective. ISC was stronger in several brain
regions--most robustly in the parahippocampal gyrus, posterior parietal cortex and lateral occipital cortex--when the participants viewed the movie with similar rather than
different perspectives. Synchronization was not explained by differences in visual
sampling of the movies, as estimated by eye gaze. We propose that synchronous brain
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activity across individuals adopting similar psychological perspectives could be an important neural mechanism supporting shared understanding of the environment.
7. Lamminmäki S, Parkkonen L, Hari R: Neuromagnetic responses to amplitudemodulated binaural tones, speech, and music. Ear and Hearing 2014, 35: 461–467.
OBJECTIVES: Auditory steady-state responses that can be elicited by various periodic
sounds inform about subcortical and early cortical auditory processing. Steady-state
responses to amplitude-modulated pure tones have been used to scrutinize binaural
interaction by frequency-tagging the two ears' inputs at different frequencies. Unlike
pure tones, speech and music are physically very complex, as they include many frequency components, pauses, and large temporal variations. To examine the utility of
magnetoencephalographic (MEG) steady-state fields (SSFs) in the study of early cortical processing of complex natural sounds, the authors tested the extent to which amplitude-modulated speech and music can elicit reliable SSFs. DESIGN: MEG responses
were recorded to 90-s-long binaural tones, speech, and music, amplitude-modulated at
41.1 Hz at four different depths (25, 50, 75, and 100%). The subjects were 11 healthy,
normal-hearing adults. MEG signals were averaged in phase with the modulation frequency, and the sources of the resulting SSFs were modeled by current dipoles. After
the MEG recording, intelligibility of the speech, musical quality of the music stimuli,
naturalness of music and speech stimuli, and the perceived deterioration caused by the
modulation were evaluated on visual analog scales. RESULTS: The perceived quality
of the stimuli decreased as a function of increasing modulation depth, more strongly
for music than speech; yet, all subjects considered the speech intelligible even at the
100% modulation. SSFs were the strongest to tones and the weakest to speech stimuli;
the amplitudes increased with increasing modulation depth for all stimuli. SSFs to
tones were reliably detectable at all modulation depths (in all subjects in the right hemisphere, in 9 subjects in the left hemisphere) and to music stimuli at 50 to 100%
depths, whereas speech usually elicited clear SSFs only at 100% depth. The hemispheric balance of SSFs was toward the right hemisphere for tones and speech, whereas SSFs to music showed no lateralization. In addition, the right lateralization of SSFs
to the speech stimuli decreased with decreasing modulation depth. CONCLUSIONS:
The results showed that SSFs can be reliably measured to amplitude-modulated natural
sounds, with slightly different hemispheric lateralization for different carrier sounds.
With speech stimuli, modulation at 100% depth is required, whereas for music the
75% or even 50% modulation depths provide a reasonable compromise between the
signal-to-noise ratio of SSFs and sound quality or perceptual requirements. SSF recordings thus seem feasible for assessing the early cortical processing of natural
sounds.
8. Lankinen K, Saari J, Hari R, Koskinen M: Intersubject consistency of cortical
MEG signals during movie viewing. NeuroImage 2014, 92: 217–224.
According to recent functional magnetic resonance imaging (fMRI) studies, spectators
of a movie may share similar spatiotemporal patterns of brain activity. We aimed to
extend these findings of intersubject correlation to temporally accurate single-trial
magnetoencephalography (MEG). A silent 15-min black-and-white movie was shown
to eight subjects twice. We adopted a spatial filtering model and estimated its parameter values by using multi-set canonical correlation analysis (M-CCA) so that the intersubject correlation was maximized. The procedure resulted in multiple (mutually unAnnual Report 2014
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correlated) time-courses with statistically significant intersubject correlations at frequencies below 10 Hz; the maximum correlation was 0.28 ± 0.075 in the ≤1 Hz band.
Moreover, the 24-Hz frame rate elicited steady-state responses with statistically significant intersubject correlations up to 0.29 ± 0.12. To assess the brain origin of the
across-subjects correlated signals, the time-courses were correlated with minimumnorm source current estimates (MNEs) projected to the cortex. The time series implied
across-subjects synchronous activity in the early visual, posterior and inferior parietal,
lateral temporo-occipital, and motor cortices, and in the superior temporal sulcus
(STS) bilaterally. These findings demonstrate the capability of the proposed methodology to uncover cortical MEG signatures from single-trial signals that are consistent
across spectators of a movie.
9. Lindsberg PJ, Castrén E, Korkeila J, Alho H, Erkinjuntti T, Isometsä E, Kalso E,
Karlsson H, Marttunen M, Pihko H, Tienari P, Wartiovaara A, Jäkälä P,
Kälviäinen R, Soininen H, Tiihonen J, Karlsson H, Rinne J, Roine RO, Elovaara I,
Tamminen T, Öhman J, Majamaa K, Hari R: Aivosairaudet ovat kalleimmat kansantautimme. Duodecim 2014, 130: 1721–1730.
Euroopan suorat terveydenhuoltokulut vuonna 2010 olivat 1 260 miljardia euroa, mistä
neljännes kului aivosairauksiin. Aivosairauksien kokonaiskulut arvioitiin nelinkertaisiksi suhteutettuna kahteen muuhun suuren kansansairausryhmään, syöpään sekä sydän- ja verisuonisairauksiin. Väestön ikääntymisen ja modernin työelämän kognitiivisten vaatimusten myötä aivosairauksien ja aivojen toimintakyvyn ylläpitämisen merkitys yhteiskunnassamme lisääntyy.
10. Malinen S, Renvall V, Hari R: Functional parcellation of the human primary somatosensory cortex to natural touch. European Journal of Neuroscience 2014, 39:
738–743.
Despite the significance of human touch, brain responses to interpersonal manual
touch have been rarely investigated. We used functional magnetic resonance imaging
to study brain activity in eight healthy adults whose left hand was touched by two individuals, in separate runs and in 20-s blocks, either by holding, smoothing, or poking.
Acceleration was measured from both the subject's and the touching person's hands for
postimaging control of the stimuli. Independent component analysis of the functional
magnetic resonance imaging data unraveled three functional networks involving the
primary somatosensory cortex (SI). One network comprised the contralateral and another the ipsilateral Brodmann area 3. The third network included area 2 bilaterally,
left-hemisphere middle temporal gyrus and dorsolateral prefrontal regions, ventral prefrontal cortices bilaterally, and middle cingulate cortex. The response shapes and polarities varied between the three networks. The contralateral area 3 differentiated the
responses between the three types of touch stimuli, and the response magnitudes depended on the variability of the touch within each block. However, the responses of
the other two networks were strikingly similar to all stimuli. The subjects' reports on
the pleasantness of the touch did not correlate with the characteristics of the SI responses. These findings imply area-specific processing of the natural human touch in
three networks including the SI cortex, with only area 2 connected to a functional network of brain areas that may support social interaction.
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11. Mandel A, Helokunnas S, Pihko E, Hari R: Neuromagnetic brain responses to other person’s eye blinks seen on video. European Journal of Neuroscience 2014, 40:
2576–2580.
Eye blinks, typically occurring 15-20 times per minute, rarely capture attention during
face-to-face interaction. To determine the extent to which eye blinks affect the viewer's brain activity, we recorded magnetoencephalographic brain responses to natural
blinks, and to the same blinks slowed down to 38% of the original speed. The stimuli
were presented on video once every 2.3-6.2 s. As a control, we presented two horizontal black bars moving with the same time courses and the same extent as the eyelids in
the blink video. Both types of blinks and bars elicited clear responses peaking at about
200 ms in the occipital areas, with no systematic differences between hemispheres. For
the bars, these main responses were (as expected) weaker (by 24%) and later (by 33
ms) to slow-motion than normal-speed stimuli. For blinks, however, the responses to
both normal-speed and slow-motion stimuli were of the same amplitude and latency.
Our results demonstrate that the brain not only responds to other persons' eye blinks,
but that the responses are as fast and of equal size even when the blinks are considerably slowed down. We interpret this finding to reflect the increased social salience of
the slowed-down blinks that counteracted the general tendency of the brain to react
more weakly and more slowly to slowly- vs. quickly-changing stimuli. This finding
may relate to the social importance of facial gestures, including eye blinks.
12. Nevalainen P, Lauronen L, Pihko E: Development of human somatosensory cortical functions – what have we learned from magnetoencephalography: A review.
Frontiers in Human Neuroscience 2014, 5: 158 (15 pages).
The mysteries of early development of cortical processing in humans have started to
unravel with the help of new non-invasive brain research tools like multichannel magnetoencephalography (MEG). In this review, we evaluate, within a wider neuroscientific and clinical context, the value of MEG in studying normal and disturbed functional development of the human somatosensory system. The combination of excellent
temporal resolution and good localization accuracy provided by MEG has, in the case
of somatosensory studies, enabled the differentiation of activation patterns from the
newborn's primary (SI) and secondary somatosensory (SII) areas. Furthermore, MEG
has shown that the functioning of both SI and SII in newborns has particular immature
features in comparison with adults. In extremely preterm infants, the neonatal MEG
response from SII also seems to potentially predict developmental outcome: those
lacking SII responses at term show worse motor performance at age 2  years than those
with normal SII responses at term. In older children with unilateral early brain lesions,
bilateral alterations in somatosensory cortical activation detected in MEG imply that
the impact of a localized insult may have an unexpectedly wide effect on cortical somatosensory networks. The achievements over the last decade show that MEG provides a unique approach for studying the development of the somatosensory system
and its disturbances in childhood. MEG well complements other neuroimaging methods in studies of cortical processes in the developing brain.
13. Nevalainen P, Rahkonen P, Pihko E, Lano A, Vanhatalo S, Andersson S, Autti T,
Valanne L, Metsäranta M, Lauronen L: Evaluation of somatosensory cortical processing in extremely preterm infants at term with MEG and EEG. Clinical Neurophysiology, online June 2014.
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OBJECTIVE: Prior studies on extremely preterm infants have reported long-term
prognostic value of absent secondary somatosensory cortex (SII) responses in magnetoencephalography (MEG) at term. The present work (i) further examines the potential
added value of SII responses in neonatal neurological evaluation of preterm infants,
and (ii) tests whether SII responses are detectable in routine neonatal electroencephalogram complemented with median nerve stimulation (EEG-SEP). METHODS: Altogether 29 infants born <28 gestational weeks underwent MEG, MRI, and neonatal
neurological examination at term age, and Hempel neurological examination at 2-years
corrected age. Term-age EEG-SEP was available for seven infants. RESULTS: While
in neonatal neurological examination severely abnormal finding predicted unfavorable
outcome in 2/2 infants, outcome was unfavorable also in 3/9 (33%) moderately abnormal and in 5/18 (28%) mildly abnormal/normal infants. Of these eight infants four
had unilaterally absent SII responses in MEG, compared with only two of the 24 infants with favorable outcome. Furthermore, SII responses (when present in MEG)
were also usually detectable in EEG-SEP. CONCLUSIONS: Complementing clinical
EEG recording with SEP holds promise for valuable extension of neonatal neurophysiological assessment. SIGNIFICANCE: Multimodal study of EEG and sensory evoked
responses is informative, safe, and cheap, and it can be readily performed at bedside.
14. Nummenmaa L, Hari R: Aivot rakastavat seuraa. Tiede 2014, April: 32–36.
Aivomme peilaavat salamannopeasti muiden aikeita ja tunteita. Sosiaalisuus on niiden
oletustila. [a popular article about two-person neuroscience and social interaction]
15. Nummenmaa L, Glerean E, Hari R, Hietanen JK: Bodily maps of emotions. Proceedings of the National Academy of Sciences of the United States of America
(PNAS) 2014, 111: 646–651.
Emotions are often felt in the body, and somatosensory feedback has been proposed to
trigger conscious emotional experiences. Here we reveal maps of bodily sensations
associated with different emotions using a unique topographical self-report method. In
five experiments, participants (n = 701) were shown two silhouettes of bodies alongside emotional words, stories, movies, or facial expressions. They were asked to color
the bodily regions whose activity they felt increasing or decreasing while viewing each
stimulus. Different emotions were consistently associated with statistically separable
bodily sensation maps across experiments. These maps were concordant across West
European and East Asian samples. Statistical classifiers distinguished emotion-specific
activation maps accurately, confirming independence of topographies across emotions.
We propose that emotions are represented in the somatosensory system as culturally
universal categorical somatotopic maps. Perception of these emotion-triggered bodily
changes may play a key role in generating consciously felt emotions.
16. Nummenmaa L, Saarimäki H, Glerean E, Gotsopoulos A, Jääskeläinen IP, Hari R,
Sams M: Emotional speech synchronizes brains across listeners and engages largescale dynamic brain networks. NeuroImage 2014, 102: 498–509.
Speech provides a powerful means for sharing emotions. Here we implement novel
intersubject phase synchronization and whole-brain dynamic connectivity measures to
show that networks of brain areas become synchronized across participants who are
listening to emotional episodes in spoken narratives. Twenty participants' hemodyAnnual Report 2014
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namic brain activity was measured with functional magnetic resonance imaging
(fMRI) while they listened to 45-s narratives describing unpleasant, neutral, and pleasant events spoken in neutral voice. After scanning, participants listened to the narratives again and rated continuously their feelings of pleasantness-unpleasantness (valence) and of arousal-calmness. Instantaneous intersubject phase synchronization
(ISPS) measures were computed to derive both multi-subject voxel-wise similarity
measures of hemodynamic activity and inter-area functional dynamic connectivity
(seed-based phase synchronization, SBPS). Valence and arousal time series were subsequently used to predict the ISPS and SBPS time series. High arousal was associated
with increased ISPS in the auditory cortices and in Broca's area, and negative valence
was associated with enhanced ISPS in the thalamus, anterior cingulate, lateral prefrontal, and orbitofrontal cortices. Negative valence affected functional connectivity of
fronto-parietal, limbic (insula, cingulum) and fronto-opercular circuitries, and positive
arousal affected the connectivity of the striatum, amygdala, thalamus, cerebellum, and
dorsal frontal cortex. Positive valence and negative arousal had markedly smaller effects. We propose that high arousal synchronizes the listeners' sound-processing and
speech-comprehension networks, whereas negative valence synchronizes circuitries
supporting emotional and self-referential processing.
17. Nummenmaa L, Smirnov D, Lahnakoski JM, Glerean E, Jääskeläinen IP, Sams M,
Hari R: Mental action simulation synchronizes action–observation circuits across
individuals. Journal of Neuroscience 2014, 34: 748–757.
A frontoparietal action-observation network (AON) has been proposed to support understanding others' actions and goals. We show that the AON "ticks together" in human subjects who are sharing a third person's feelings. During functional magnetic
resonance imaging, 20 volunteers watched movies depicting boxing matches passively
or while simulating a prespecified boxer's feelings. Instantaneous intersubject phase
synchronization (ISPS) was computed to derive multisubject voxelwise similarity of
hemodynamic activity and inter-area functional connectivity. During passive viewing,
subjects' brain activity was synchronized in sensory projection and posterior temporal
cortices. Simulation induced widespread increase of ISPS in the AON (premotor, posterior parietal, and superior temporal cortices), primary and secondary somatosensory
cortices, and the dorsal attention circuits (frontal eye fields, intraparietal sulcus).
Moreover, interconnectivity of these regions strengthened during simulation. We propose that sharing a third person's feelings synchronizes the observer's own brain mechanisms supporting sensations and motor planning, thereby likely promoting mutual
understanding.
18. Pihko E, Nevalainen P, Vaalto S, Laaksonen K, Mäenpää H, Valanne L, Lauronen
L: Reactivity of sensorimotor oscillations is altered in children with hemiplegic
cerebral palsy. Human Brain Mapping 2014, 35: 4105–4117.
Cerebral palsy (CP) is characterized by difficulty in control of movement and posture
due to brain damage during early development. In addition, tactile discrimination deficits are prevalent in CP. To study the function of somatosensory and motor systems in
CP, we compared the reactivity of sensorimotor cortical oscillations to median nerve
stimulation in 12 hemiplegic CP children vs. 12 typically developing children using
magnetoencephalography. We also determined the primary cortical somatosensory and
motor representation areas of the affected hand in the CP children using somatosensoAnnual Report 2014
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ry-evoked magnetic fields and navigated transcranial magnetic stimulation, respectively. We hypothesized that the reactivity of the sensorimotor oscillations in alpha (10
Hz) and beta (20 Hz) bands would be altered in CP and that the beta-band reactivity
would depend on the individual pattern of motor representation. Accordingly, in children with CP, suppression and rebound of both oscillations after stimulation of the
contralateral hand were smaller in the lesioned than intact hemisphere. Furthermore, in
two of the three children with CP having ipsilateral motor representation, the beta- but
not alpha-band modulations were absent in both hemispheres after affected hand stimulation suggesting abnormal sensorimotor network interactions in these individuals.
The results are consistent with widespread alterations in information processing in the
sensorimotor system and complement current understanding of sensorimotor network
development after early brain insults. Precise knowledge of the functional sensorimotor network organization may be useful in tailoring individual rehabilitation for people
with CP.
19. Raij TT, Korkeila J, Joutsenniemi K, Saarni SI, Riekki TJJ: Association of stigma
resistance with emotion regulation — Functional magnetic resonance imaging and
neuropsychological findings. Comprehensive Psychiatry 2014, 55: 727–735.
BACKGROUND: [corrected] Personal characteristics contribute to whether negative
attitudes in society are internalized as deteriorating self-stigma. Studies in healthy subjects suggest that resilience is associated with the regulation of amygdala activation by
the medial prefrontal cortex (mPFC), but little is known about the factors that contribute to individual stigma resistance in psychiatric patients. METHODS: We assessed
stigma (by measuring association strengths between social inferiority and schizophrenia by an implicit association test) in 20 patients with schizophrenia and in 16 age- and
sex-matched healthy control subjects. The brain activation strengths were measured by
functional magnetic resonance imaging during evaluation of schizophrenia-related
statements and of control statements. RESULTS: Association strengths between social
inferiority and schizophrenia were inversely related to the strength of the activation of
the rostro-ventral mPFC. This inverse correlation survived adjustment for global functioning, depression symptom scores, and insight. Activation of the rostro-ventral
mPFC was negatively correlated with activation of the amygdala. The association
strengths between social inferiority and schizophrenia correlated with the compromised performance in a Stroop task, which is a measure of cognitive regulation.
DISCUSSION: Our findings suggest that individual stigma resistance is associated
with emotion regulation. These findings may help to understand better stigma resistance and thereby aid the development of patient interventions that add to the public
anti-stigma work in reducing devastating effects of stigma.
20. Ramkumar P, Parkkonen L, Hyvärinen A: Group-level spatial independent component analysis of Fourier envelopes of resting-state MEG data. NeuroImage 2014,
86: 480–491.
We developed a data-driven method to spatiotemporally and spectrally characterize the
dynamics of brain oscillations in resting-state magnetoencephalography (MEG) data.
The method, called envelope spatial Fourier independent component analysis (eSFICA), maximizes the spatial and spectral sparseness of Fourier energies of a cortically constrained source current estimate. We compared this method using a simulated
data set against 5 other variants of independent component analysis and found that eSAnnual Report 2014
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FICA performed on par with its temporal variant, eTFICA, and better than other ICA
variants, in characterizing dynamics at time scales of the order of minutes. We then
applied eSFICA to real MEG data obtained from 9 subjects during rest. The method
identified several networks showing within- and cross-frequency inter-areal functional
connectivity profiles which resemble previously reported resting-state networks, such
as the bilateral sensorimotor network at ~20Hz, the lateral and medial parieto-occipital
sources at ~10 Hz, a subset of the default-mode network at ~8 and ~15Hz, and lateralized temporal lobe sources at ~8Hz. Finally, we interpreted the estimated networks as
spatiospectral filters and applied the filters to obtain the dynamics during a natural
stimulus sequence presented to the same 9 subjects. We observed occipital alpha modulation to visual stimuli, bilateral rolandic mu modulation to tactile stimuli and video
clips of hands, and the temporal lobe network modulation to speech stimuli, but no
modulation of the sources in the default-mode network. We conclude that (1) the proposed method robustly detects inter-areal cross-frequency networks at long time
scales, (2) the functional relevance of the resting-state networks can be probed by applying the obtained spatiospectral filters to data from measurements with controlled
external stimulation.
21. Renvall V, Nangini C, Hari R: All that glitters is not BOLD: inconsistencies in
functional MRI. Scientific Reports 2014, 4: 3920.
The blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) signal is a widely-accepted marker of brain activity. The acquisition parameters (APs) of fMRI aim at maximizing the signals related to neuronal activity
while minimizing unrelated signal fluctuations. Currently, a diverse set of APs is used
to acquire BOLD fMRI data. Here we demonstrate that some fMRI responses are
alarmingly inconsistent across APs, ranging from positive to negative, or disappearing
entirely, under identical stimulus conditions. These discrepancies, resulting from nonBOLD effects masquerading as BOLD signals, have remained largely unnoticed because studies rarely employ more than one set of APs. We identified and characterized
non-BOLD responses in several brain areas, including posterior cingulate cortex and
precuneus, as well as AP-dependence of both the signal time courses and of seedbased functional networks, noticing that AP manipulation can inform about the origin
of the measured signals.
22. Riekki T, Lindeman M, Raij TT: Supernatural believers attribute more intentions
to random movement than skeptics: An fMRI study. Social Neuroscience 2014, 9:
400–411.
A host of research has attempted to explain why some believe in the supernatural and
some do not. One suggested explanation for commonly held supernatural beliefs is that
they are a by-product of theory of mind (ToM) processing. However, this does not explain why skeptics with intact ToM processes do not believe. We employed fMRI to
investigate activation differences in ToM-related brain circuitries between supernatural
believers (N = 12) and skeptics (N = 11) while they watched 2D animations of geometric objects moving intentionally or randomly and rated the intentionality of the animations. The ToM-related circuitries in the medial prefrontal cortex (mPFC) were localized by contrasting intention-rating-related and control-rating-related brain activation. Compared with the skeptics, the supernatural believers rated the random movements as more intentional and had stronger activation of the ToM-related circuitries
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during the animation with random movement. The strength of the ToM-related activation covaried with the intentionality ratings. These findings provide evidence that differences in ToM-related activations are associated with supernatural believers' tendency to interpret random phenomena in mental terms. Thus, differences in ToM processing may contribute to differences between believing and unbelieving.
23. Wens V, Bourguignon M, Goldman S, Marty B, Op de Beeck M, Clumeck C,
Mary A, Peigneux P, Van Bogaert P, Brookes MJ, De Tiege X: Inter- and intrasubject variability of neuromagnetic resting state networks. Brain Topography
2014, 27: 620–634.
Functional connectivity studies conducted at the group level using magnetoencephalography (MEG) suggest that resting state networks (RSNs) emerge from the largescale envelope correlation structure within spontaneous oscillatory brain activity.
However, little is known about the consistency of MEG RSNs at the individual level.
This paper investigates the inter- and intra-subject variability of three MEG RSNs
(sensorimotor, auditory and visual) using seed-based source space envelope correlation
analysis applied to 5 min of resting state MEG data acquired from a 306-channel
whole-scalp neuromagnetometer (Elekta Oy, Helsinki, Finland) and source projected
with minimum norm estimation. The main finding is that these three MEG RSNs exhibit substantial variability at the single-subject level across and within individuals,
which depends on the RSN type, but can be reduced after averaging over subjects or
sessions. Over- and under-estimations of true RSNs variability are respectively obtained using template seeds, which are potentially mislocated due to inter-subject variations, and a seed optimization method minimizing variability. In particular, bounds on
the minimal number of subjects or sessions required to obtain highly consistent between- or within-subject averages of MEG RSNs are derived. Furthermore, MEG RSN
topography positively correlates with their mean connectivity at the inter-subject level.
These results indicate that MEG RSNs associated with primary cortices can be robustly extracted from seed-based envelope correlation and adequate averaging. MEG thus
appears to be a valid technique to compare RSNs across subjects or conditions, at least
when using the current methods.
24. Wens V, Mary A, Bourguignon M, Goldman S, Marty B, de Beeck M O, Van Bogaert P, Peigneux P, De Tiege X: About the electrophysiological basis of resting
state networks. Clinical Neurophysiology 2014, 125: 1711–1713 (commentary letter with no abstract).
MULTIMODAL NEUROIMAGING, SIGNAL ANALYSIS, AND
MODELING
Person years: 0.4 professor, 0.2 postdocs
1. Gramfort A, Luessi M, Larson E, Engemann D, Strohmeier D, Brodbeck C, Parkkonen L, Hämäläinen M: MNE software for processing MEG and EEG data. NeuroImage 2014, 86: 446–460.
Magnetoencephalography and electroencephalography (M/EEG) measure the weak
electromagnetic signals originating from neural currents in the brain. Using these signals to characterize and locate brain activity is a challenging task, as evidenced by
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several decades of methodological contributions. MNE, whose name stems from its
capability to compute cortically-constrained minimum-norm current estimates from
M/EEG data, is a software package that provides comprehensive analysis tools and
workflows including preprocessing, source estimation, time–frequency analysis, statistical analysis, and several methods to estimate functional connectivity between distributed brain regions. The present paper gives detailed information about the MNE package and describes typical use cases while also warning about potential caveats in analysis. The MNE package is a collaborative effort of multiple institutes striving to implement and share best methods and to facilitate distribution of analysis pipelines to
advance reproducibility of research. Full documentation is available at
http://martinos.org/mne.
IMAGING LANGUAGE
Person years: 1 professor, 6.5 postdocs, 4 PhD students
1. Helenius P, Sivonen P, Parviainen T, Isoaho P, Hannus S, Kauppila T, Salmelin R,
Isotalo L: Abnormal functioning of the left temporal lobe in language-impaired
children. Brain and Language 2014, 130: 11–18.
Specific language impairment is associated with enduring problems in languagerelated functions. We followed the spatiotemporal course of cortical activation in SLI
using magnetoencephalography. In the experiment, children with normal and impaired
language development heard spoken real words and pseudowords presented only once
or two times in a row. In typically developing children, the activation in the bilateral
superior temporal cortices was attenuated to the second presentation of the same word.
In SLI children, this repetition effect was nearly nonexistent in the left hemisphere.
Furthermore, the activation was equally strong to words and pseudowords in SLI children whereas in the typically developing children the left hemisphere activation persisted longer for pseudowords than words. Our results indicate that the short-term
maintenance of linguistic activation that underlies spoken word recognition is defective in SLI particularly in the left language-dominant hemisphere. The unusually rapid
decay of speech-evoked activation can contribute to impaired vocabulary growth.
2. Hultén A, Karvonen L, Laine M, Salmelin R: Producing speech with a newly
learned morphosyntax and vocabulary: An magnetoencephalography study. Journal of Cognitive Neuroscience 2014, 26: 1721–1735.
Ten participants learned a miniature language (Anigram), which they later employed
to verbally describe a pictured event. Using magnetoencephalography, the cortical dynamics of sentence production in Anigram was compared with that in the native
tongue from the preparation phase up to the production of the final word. At the preparation phase, a cartoon image with two animals prompted the participants to plan either
the corresponding simple sentence (e.g., “the bear hits the lion”) or a grammar-free list
of the two nouns (“the bear, the lion”). For the newly learned language, this stage induced stronger left angular and adjacent inferior parietal activations than for the native
language, likely reflecting a higher load on lexical retrieval and STM storage. The
preparation phase was followed by a cloze task where the participants were prompted
to produce the last word of the sentence or word sequence. Production of the sentencefinal word required retrieval of rule-based inflectional morphology and was accompaAnnual Report 2014
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nied by increased activation of the left middle superior temporal cortex that did not
differ between the two languages. Activation of the right temporal cortex during the
cloze task suggested that this area plays a role in integrating word meanings into the
sentence frame. The present results indicate that, after just a few days of exposure, the
newly learned language harnesses the neural resources for multiword production much
the same way as the native tongue and that the left and right temporal cortices seem to
have functionally different roles in this processing.
3. Kim CH, Lee S, Kim JS, Seol J, Yi SW, Chung CK: Melody effects on ERANm
elicited by harmonic irregularity in musical syntax. Brain Research 2014, 1560:
36–45.
Recent studies have reported that early right anterior negativity (ERAN) and its magnetic counterpart (ERANm) are evoked by harmonic irregularity in Western tonal music; however, those studies did not control for differences of melody. Because melody
and harmony have an interdependent relationship and because melody (in this study
melody is represented by the highest voice part) in a chord sequence may dominate,
there is controversy over whether ERAN (or ERANm) changes arise from melody or
harmony differences. To separate the effects of melody differences and harmonic irregularity on ERANm responses, we designed two magnetoencephalography experiments and behavioral test. Participants were presented with three types of chord progression sequences (Expected, Intermediate, and Unexpected) with different harmonic
regularities in which melody differences were or were not controlled. In the uncontrolled melody difference experiment, the unexpected chord elicited a significantly
largest ERANm, but in the controlled melody difference experiment, the amplitude of
the ERANm peak did not differ among the three conditions. However, ERANm peak
latency was delayed more than that in the uncontrolled melody difference experiment.
The behavioral results show the difference between the two experiments even if harmonic irregularity was discriminated in the uncontrolled melody difference experiment. In conclusion, our analysis reveals that there is a relationship between the effects
of harmony and melody on ERANm. Hence, we suggest that a melody difference in a
chord progression is largely responsible for the observed changes in ERANm, reaffirming that melody plays an important role in the processing of musical syntax.
4. Kujala J, Sudre G, Vartiainen J, Liljeström M, Mitchell T, Salmelin R: Multivariate analysis of correlation between electrophysiological and hemodynamic responses during cognitive processing. NeuroImage 2014, 92: 207–216.
Animal and human studies have frequently shown that in primary sensory and motor
regions the BOLD signal correlates positively with high-frequency and negatively with
low-frequency neuronal activity. However, recent evidence suggests that this relationship may also vary across cortical areas. Detailed knowledge of the possible spectral
diversity between electrophysiological and hemodynamic responses across the human
cortex would be essential for neural-level interpretation of fMRI data and for informative multimodal combination of electromagnetic and hemodynamic imaging data, especially in cognitive tasks. We applied multivariate partial least squares correlation
analysis to MEG–fMRI data recorded in a reading paradigm to determine the correlation patterns between the data types, at once, across the cortex. Our results revealed
heterogeneous patterns of high-frequency correlation between MEG and fMRI reAnnual Report 2014
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sponses, with marked dissociation between lower and higher order cortical regions.
The low-frequency range showed substantial variance, with negative and positive correlations manifesting at different frequencies across cortical regions. These findings
demonstrate the complexity of the neurophysiological counterparts of hemodynamic
fluctuations in cognitive processing.
5. Ylinen S, Nora A, Leminen A, Hakala T, Huotilainen M, Shtyrov Y, Mäkelä JP,
Service E: Two distinct auditory-motor circuits for monitoring speech production
as revealed by rehearsal-elicited suppression of auditory cortex. Cerebral Cortex,
online January 2014.
Speech production, both overt and covert, down-regulates the activation of auditory
cortex. This is thought to be due to forward prediction of the sensory consequences of
speech, contributing to a feedback control mechanism for speech production. Critically, however, these regulatory effects should be specific to speech content to enable accurate speech monitoring. To determine the extent to which such forward prediction is
content-specific, we recorded the brain’s neuromagnetic responses to heard multisyllabic pseudowords during covert rehearsal in working memory, contrasted with a control task. The cortical auditory processing of target syllables was significantly suppressed during rehearsal compared with control, but only when they matched the rehearsed items. This critical specificity to speech content enables accurate speech monitoring by forward prediction, as proposed by current models of speech production. The
one-to-one phonological motor-to-auditory mappings also appear to serve the maintenance of information in phonological working memory. Further findings of righthemispheric suppression in the case of whole-item matches and left-hemispheric enhancement for last-syllable mismatches suggest that speech production is monitored by
2 auditory-motor circuits operating on different timescales: Finer grain in the left versus coarser grain in the right hemisphere. Taken together, our findings provide hemisphere-specific evidence of the interface between inner and heard speech.
VISUAL COGNITION AND AWARENESS
Person years: 0.2 docent, 1 postdoc, 3 PhD students
1. Bona S, Silvanto J: Accuracy and confidence of visual short-term memory do not
go hand-in-hand: behavioral and neural dissociations. PLoS One 2014, 9: e90808.
Currently influential models of working memory posit that memory content is highly
accessible to conscious inspection. These models predict that metacognition of
memory performance should go hand-in-hand with the accuracy of the underlying
memory representation. To test this view, we investigated how visual information presented during the maintenance period affects VSTM accuracy and confidence. We
used a delayed cue-target orientation discrimination task in which participants were
asked to hold in memory a grating, and during the maintenance period a second
memory cue could be presented. VSTM accuracy of the first memory cue was impaired when the orientation of the second memory cue was sufficiently different.
However, participants' response confidence was reduced whenever the second memory
cue was presented; thus VSTM accuracy and confidence were dissociated. In a second
experiment, we applied transcranial direct current stimulation (tDCS) over the right
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dorsolateral prefrontal cortex (DLPFC) to investigate the causal role of this region in
VSTM metacognition. Relative to the sham condition, anodal tDCS induced a general
reduction in confidence ratings but did not affect VSTM accuracy. Overall, these results indicate that our metacognition of memory performance is influenced by factors
other than the accuracy of the underlying memory representation.
2. Bona S, Herbert A, Toneatto C, Silvanto J, Cattaneo Z: The causal role of the lateral occipital complex in visual mirror symmetry detection and grouping: an fMRIguided TMS study. Cortex 2014, 51: 46–55.
Despite the fact that bilateral mirror symmetry is an important characteristic of the
visual world, few studies have investigated its neural basis. Here we addressed this
issue by investigating whether the object-selective lateral occipital (LO) cortex, a key
brain region in object and shape processing, is causally involved in bilateral symmetry
detection. Participants were asked to discriminate between symmetric and asymmetric
dot patterns, while fMRI-guided repetitive TMS was delivered online over either the
left LO, the right LO or two control sites in the occipital cortex. We found that the application of TMS over both right and left LO impaired symmetry judgments, with disruption being greater following right LO than left LO TMS, indicative of right hemisphere lateralization in symmetry processing. TMS over LO bilaterally also affected a
visual contour detection task, with no evidence for hemispheric difference in this task.
Overall, our results demonstrates that LO bilaterally plays a causal role in symmetry
detection possibly due to symmetry acting as a strong cue in Gestalt processes mediating object recognition.
3. Cattaneo Z, Bona S, Bauer C, Silvanto J, Herbert AM, Vecchi T, Merabet LB:
Symmetry detection in visual impairment: Behavioral evidence and neural correlates. Symmetry 2014, 6: 427–443.
Bilateral symmetry is an extremely salient feature for the human visual system. An
interesting issue is whether the perceptual salience of symmetry is rooted in normal
visual development. In this review, we discuss empirical work on visual and tactile
symmetry detection in normally sighted and visually impaired individuals. On the one
hand, available evidence suggests that efficient visual symmetry detection may need
normal binocular vision development. On the other hand, converging evidence suggests that symmetry can develop as a principle of haptic perceptual organization in individuals lacking visual experience. Certain features of visual symmetry detection,
however, such as the higher salience of the patterns containing a vertical axis of symmetry, do not systematically apply to the haptic modality. The neural correlates (revealed with neuroimaging) associated with visual and haptic symmetry detection are
also discussed.
4. Cattaneo Z, Bona S, Monegato M, Pece A, Vecchi T, Herbert AM, Merabet LB:
Visual symmetry perception in early onset monocular blindness. Visual Cognition
2014, 22: 963–974.
Symmetry detection is impaired by abnormal binocular vision development such as in
amblyopia. However, the detection of symmetry has never been investigated in cases
where input from one eye is profoundly compromised. Testing monocularly blind
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(MB) individuals represents a unique opportunity to investigate whether symmetry salience relies on a normally developed binocular visual system. In a visual symmetry
detection task using dot patterns, congenitally MB showed comparable accuracy to
normally sighted individuals viewing monocularly. This included better detection of
vertically than horizontally symmetric patterns. However, the MB were slower than
controls in detecting a symmetrical pattern. In a control target-detection task, no significant differences in performance were observed between these groups. Overall,
normal developing binocular vision does not appear necessary for the visual system to
detect the presence of visual symmetry. However, optimal detection mechanisms may
be dependent on binocular summation or other processes dependent on input from both
eyes.
5. Cattaneo Z, Renzi C, Bona S, Merabet LB, Carbon CC, Vecchi T: Hemispheric
asymmetry in discriminating faces differing for featural or configural (secondorder relations) aspects. Psychonomic Bulletin and Review 2014, 21: 363–369.
The human capacity to discriminate among different faces relies on distinct parallel
subprocesses, based either on the analysis of configural aspects or on the sequential
analysis of the single elements of a face. A particular type of configural processing
consists of considering whether two faces differ in terms of internal spacing among
their features, referred to as second-order relations processing. Findings from electrophysiological, neuroimaging, and lesion studies suggest that, overall, configural processes rely more on the right hemisphere, whereas analysis of single features would
involve more the left. However, results are not always consistent, and behavioral evidence for a right-hemisphere specialization in second-order relations processing is
lacking. Here, we used divided visual field presentation to investigate the possible different contributions of the two hemispheres to face discrimination based on relational
versus featural processing. Our data indicate a right-hemispheric specialization in relational processing of upright (but not inverted) faces. Furthermore, we provide evidence
regarding the involvement of both the right and left hemispheres in the processing of
faces differing for inner features, suggesting that both analytical and configural modes
of processing are at play.
6. Cattaneo Z, Renzi C, Casali S, Silvanto J, Vecchi T, Papagno C, D'Angelo E: Cerebellar vermis plays a causal role in visual motion discrimination. Cortex 2014, 58:
272–280.
Cerebellar patients have been found to show deficits in visual motion discrimination,
suggesting that the cerebellum may play a role in visual sensory processing beyond
mediating motor control. Here we show that triple-pulse online transcranial magnetic
stimulation (TMS) over cerebellar vermis but not over the cerebellar hemispheres significantly impaired motion discrimination. Critically, the interference caused by vermis TMS on motion discrimination did not depend on an indirect effect of TMS over
nearby visual areas, as demonstrated by a control experiment in which TMS over V1
but not over cerebellar vermis significantly impaired orientation discrimination. These
findings demonstrate the causal role of the cerebellar vermis in visual motion processing in neurologically normal participants.
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7. Renzi C, Vecchi T, D' Angelo E, Silvanto J, Cattaneo Z: Phosphene induction by
cerebellar transcranial magnetic stimulation. Clinical Neurophysiology 2014, 125:
2132–2133.
[No abstract]
8. Salminen-Vaparanta N, Vanni S, Noreika V, Valiulis V, Móró L, Revonsuo A:
Subjective characteristics of TMS-induced phosphenes originating in human V1
and V2. Cerebral Cortex 2014, 24: 2751–2760.
One way to study the neural correlates of visual consciousness is to localize the cortical areas whose stimulation generates subjective visual sensations, called phosphenes.
While there is support for the view that the stimulation of several different visual areas
in the occipital lobe may produce phosphenes, it is not clear what the contribution of
each area is. Here, we studied the roles of the primary visual cortex (V1) and the adjacent area V2 in eliciting phosphenes by using functional magnetic resonance imagingguided transcranial magnetic stimulation (TMS) combined with spherical modeling of
the TMS-induced electric field. Reports of the subjective visual features of phosphenes
were systematically collected and analyzed. We found that selective stimulation of V1
and V2 are equally capable of generating phosphenes, as demonstrated by comparable
phosphene thresholds and similar characteristics of phosphene shape, color, and texture. However, the phosphenes induced by V1 stimulation were systematically perceived as brighter than the phosphenes induced by the stimulation of V2. Thus, these
results suggest that V1 and V2 have a similar capability to produce conscious percepts.
Nevertheless, V1 and V2 contribute differently to brightness: neural activation originating in V1 generates a more intense sensation of brightness than similar activation
originating in V2.
9. Silvanto J: Why is "blindsight" blind? A new perspective on primary visual cortex,
recurrent activity and visual awareness. Consciousness and Cognition 2014.
The neuropsychological phenomenon of blindsight has been taken to suggest that the
primary visual cortex (V1) plays a unique role in visual awareness, and that extrastriate activation needs to be fed back to V1 in order for the content of that activation to
be consciously perceived. The aim of this review is to evaluate this theoretical framework and to revisit its key tenets. Firstly, is blindsight truly a dissociation of awareness
and visual detection? Secondly, is there sufficient evidence to rule out the possibility
that the loss of awareness resulting from a V1 lesion simply reflects reduced extrastriate responsiveness, rather than a unique role of V1 in conscious experience? Evaluation of these arguments and the empirical evidence leads to the conclusion that the loss
of phenomenal awareness in blindsight may not be due to feedback activity in V1 being the hallmark awareness. On the basis of existing literature, an alternative explanation of blindsight is proposed. In this view, visual awareness is a "global" cognitive
function as its hallmark is the availability of information to a large number of perceptual and cognitive systems; this requires inter-areal long-range synchronous oscillatory
activity. For these oscillations to arise, a specific temporal profile of neuronal activity
is required, which is established through recurrent feedback activity involving V1 and
the extrastriate cortex. When V1 is lesioned, the loss of recurrent activity prevents inter-areal networks on the basis of oscillatory activity. However, as limited amount of
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input can reach extrastriate cortex and some extrastriate neuronal selectivity is preserved, computations involving comparison of neural firing rates within a cortical area
remain possible. This enables "local" read-out from specific brain regions, allowing
for the detection and discrimination of basic visual attributes. Thus blindsight is blind
due to lack of "global" long-range synchrony, and it functions via "local" neural
readout from extrastriate areas.
10. Silvanto J: Is primary visual cortex necessary for visual awareness?. Trends in
Neurosciences 2014, 37: 618–619.
Influential models propose that conscious experience of extrastriate activity requires
the integrity of primary visual cortex (V1). A new study challenges this view by
demonstrating that when V1 is lesioned, visual qualia can be induced when transcranial magnetic stimulation (TMS) is applied over the patients' ipsilesional hemisphere.
11. Soto D, Silvanto J: Reappraising the relationship between working memory and
conscious awareness. Trends in Cognitive Sciences 2014, 18: 520–525.
Classically, the operation of working memory (WM) has been strongly coupled with
conscious states; it is thought that WM operates on conscious input and that we are
conscious of the contents and operations of WM. Here, we re-evaluate the relationship
between WM and conscious awareness in light of current data and question the views
that awareness is mandatory for the operation of WM and that WM contents are necessarily linked to experiential states that are consciously accessible for perceptual report.
We propose a novel framework for the relationship between WM and conscious
awareness.
OTHER
AIVOAALTO work with BRU affiliations but not directly associated to the above
BRU teams’ work
1. Hytönen K: Neuroscientific evidence for contextual effects in decision making.
Behavioral and Brain Sciences 2014, 37: 33–34.
Both internal and external states can cause inconsistencies in decision behavior. I present examples from behavioral decision-making literature and review neuroscientific
knowledge on two contextual influences: framing effects and social conformity. The
brain mechanisms underlying these behavioral adjustments comply with the dualprocess account and simple learning mechanisms, and are weak indicators for unintentionality in decision-making processes.
2. Hytönen K, Baltussen G, van den Assem MJ, Klucharev V, Sanfey AG, Smidts A:
Path dependence in risky choice: Affective and deliberative processes in brain and
behavior. Journal of Economic Behavior & Organization 2014, 107: 566–581.
Decision-makers show an increased risk appetite when they gamble with previously
won money, the house money effect, and when they have a chance to make up for a
prior loss, the break even effect. To explore the origins of these effects, we use funcAnnual Report 2014
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tional magnetic resonance imaging to record the brain activities of subjects while they
make sequential risky choices. The behavioral data from our experiment confirm the
path dependence of choices, despite the short trial duration and the many task repetitions required for neuroimaging. The brain data yield evidence that the increased risk
appetite after gains and losses is related to an increased activity of affective brain processes and a decreased activity of deliberative brain processes.
3. Tuominen L, Nummenmaa L, Keltikangas-Järvinen L, Raitakari O, Hietala J:
Mapping neurotransmitter networks with PET: An example on serotonin and opioid systems. Human Brain Mapping 2014, 35: 1875–1884.
All functions of the human brain are consequences of altered activity of specific neural
pathways and neurotransmitter systems. Although the knowledge of "system level"
connectivity in the brain is increasing rapidly, we lack "molecular level" information
on brain networks and connectivity patterns. We introduce novel voxel-based positron
emission tomography (PET) methods for studying internal neurotransmitter network
structure and intercorrelations of different neurotransmitter systems in the human
brain. We chose serotonin transporter and µ-opioid receptor for this analysis because
of their functional interaction at the cellular level and similar regional distribution in
the brain. Twenty-one healthy subjects underwent two consecutive PET scans using
[(11)C]MADAM, a serotonin transporter tracer, and [(11)C]carfentanil, a µ-opioid receptor tracer. First, voxel-by-voxel "intracorrelations" (hub and seed analyses) were
used to study the internal structure of opioid and serotonin systems. Second, voxellevel opioid-serotonin intercorrelations (between neurotransmitters) were computed.
Regional µ-opioid receptor binding potentials were uniformly correlated throughout
the brain. However, our analyses revealed nonuniformity in the serotonin transporter
intracorrelations and identified a highly connected local network (midbrain-striatumthalamus-amygdala). Regionally specific intercorrelations between the opioid and serotonin tracers were found in anteromedial thalamus, amygdala, anterior cingulate cortex, dorsolateral prefrontal cortex, and left parietal cortex, i.e., in areas relevant for
several neuropsychiatric disorders, especially affective disorders. This methodology
enables in vivo mapping of connectivity patterns within and between neurotransmitter
systems. Quantification of functional neurotransmitter balances may be a useful approach in etiological studies of neuropsychiatric disorders and also in drug development as a biomarker-based rationale for targeted modulation of neurotransmitter networks.
4. Orava J, Nummenmaa L, Noponen T, Viljanen T, Parkkola R, Nuutila P, Virtanen
KA: Brown adipose tissue function is accompanied by cerebral activation in lean
but not in obese humans. Journal of Cerebral Blood Flow & Metabolism 2014, 34:
1018–1023.
Brown adipose tissue (BAT) is able to generate heat and dissipate energy in response
to cold exposure in mammals. It has recently been acknowledged that adult humans
also have functional BAT, whose metabolic activity is reduced in obesity. In healthy
humans, the cerebral mechanisms that putatively control BAT function are unclear. By
using positron emission tomography (PET), we showed that cold-induced BAT activation is associated with glucose metabolism in the cerebellum, thalamus, and cingulate,
temporoparietal, lateral frontal, and occipital cortices in lean participants, whereas no
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such associations were found under warm control conditions. The cold-induced increase in cerebral glucose metabolism was more robust in lean than obese participants.
Cerebral glucose metabolism was not associated with skeletal muscle or white adipose
tissue glucose uptake under warm or cold conditions. In conclusion, BAT metabolism
was accompanied by the activation of specific cerebral regions, and this shows an uncharacterized role that the brain plays in the regulation of BAT function. In obese participants, the cold-induced response in cerebral activity was attenuated that provides a
clue for obesity-induced impairment in BAT metabolism.
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TEACHING ACTIVITIES
COURSES IN LOW TEMPERATURE AND NANOPHYSICS
Experimental Methods in Physics (Tfy-3.4411)
Lecturer: Prof. Mika Sillanpää
Fysiikan ja matematiikan menetelmien studio (SCI-C0200)
Lecturer/Laboratory assignments: Prof. Mika Sillanpää
Low Temperature Physics: Nanoelectronics (PHYS-E0551)
Lecturer: Doc. Sorin Paraoanu
Research Seminar in Low Temperature Physics (Tfy-3.4850)/
Individual Studies in Physics: Nano Seminar and Seminar on Low Temperature Quantum Systems (PHYS-E0544)
Coordinators: Doc. Vladimir Eltsov, Doc. Sorin Paraoanu
Special Course in Physics P: Carbon Nanomaterials (Tfy-3.4510)
LTL lecturer: Prof. Pertti Hakonen
Special Course in Theoretical Physics V: Stochastic Energetics (PHYS-E0542)
LTL lecturer: Prof. Jukka Pekola
Teknillisen fysiikan laboratoriotyöt (PHYS-C0310)
Coordinator: Doc. Juha Tuoriniemi
Assistant: M.Sc. Jukka-Pekka Kaikkonen
Quantum Physics (Tfy-3.4323)
Lecturer: Doc. Sorin Paraoanu
COURSES IN BRAIN RESEARCH
Aivoaakkoset (BECS-C3001)
BRU lecturers: Prof. Synnöve Carlson, Prof. Riitta Hari, Prof. Riitta Salmelin, and
Ph.D. Harri Piitulainen
Advanced Course on Human Brain Functioning (Tfy-99.3720)
BRU lecturer: Prof. Synnöve Carlson
Brain Imaging Practice (BECS-114.5792)
BRU lecturers: Ph.D. Jan Kujala and Ph.D. Mia Liljeström
The course utilized ANI-infrastructure
Special course in Brain and Mind Study V: TMS workshop (BECS-E3060)
BRU lecturer: Prof. Synnöve Carlson
RESEARCH SEMINARS IN LOW TEMPERATURE PHYSICS
AND NANOPHYSICS
Caspar F. Ockeloen, Department of Physics, University of Basel, Switzerland, Quantum metrology with a scanning probe atom interferometer, Jan 10
Maria Korppi, Department of Physics, University of Basel, Switzerland, Optomechanical coupling between ultra cold atoms and a membrane oscillator, Jan 10
Annual Report 2014
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Alexander Melnikov, Institute for Physics of Microstructures, Russian Academy of
Sciences, Russia, Electronic structure of pinned vortices in type-II superconductors,
Jan 16
Andrew Cleland, University of California at Santa Barbara, U.S.A., The UC Santa
Barbara Quantum Computing Effort, Jan 21
Andreas Isacsson, Chalmers University, Sweden, Lecture on NEMS modeling, Jan 23
Vladimir Dmitriev, Kapitza Insitute, Moscow, Russia, Superfluid 3He in "ordered"
aerogel, Jan 27
Andreas Isacsson, Chalmers University, Sweden, Lecture on NEMS modeling, Jan 27
Pauli Virtanen, O.V. Lounasmaa Lab, Aalto University, Finland, Time-dependent
heat transport in transparent superconducting junctions, Jan 30
Mikko Möttönen, Department of Applied Physics, Aalto University, Finland, Singleelectron pumping with silicon quantum dots, Feb 6
Pasi Lähteenmäki, O.V. Lounasmaa Laboratory, Aalto University, Finland, Experimental results on 3-frequency microwave correlations produced by a metamaterial
cavity, Feb 13
Olli-Pentti Saira, Kavli Institute of Nanoscience, Delft University of Technology,
Netherlands, Quantum computing with the ``Delftse´´ 2D transmon architecture: three
and five-qubit algorithms, Feb 20
Jaakko Sulkko, O.V. Lounasmaa Laboratory, Aalto University, Finland, Possible design and measurement improvements for the study of nanomechanical resonators coupled to a superconducting microwave cavity, Feb 27
Matti Tomi, O.V. Lounasmaa Laboratory, Aalto University, Finland, Tunable resonators of graphene and diamond-like carbon, Mar 6
Andrei Zaikin, Institute of Nanotechnology, Karlsruhe Institute of Technology, Germany and I.E.Tamm Department of Theoretical Physics, P.N. Lebedev Physics Insitute, Russia, Quantum Decoherence of Cooper Pairs, Mar 11
Matthias Staudt, Chalmers University of Technology, Sweden, Hybrid quantum systems: from quantum optics to superconducting circuits, Mar 17
Andrew Semenov, P.N. Lebedev Physics Institute, Moscow, Russia, Persistent currents in quantum phase slip rings, Mar 20
Adalberto Brunetti, Università degli Studi di Bari, Italy, Optical Stark Effect and
Dressed Exciton States in a Mn-Doped CdTe Quantum Dot, Mar 24
Mihail Silaev, O.V. Lounasmaa Laboratory, Aalto University, Finland, Lindblad
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equation approach for the the energy fluctuations in driven quantum systems, Mar 27
Matthias Meschke, O.V. Lounasmaa Laboratory, Aalto University, Finland, Applications for cutting-edge lithography with the new Vistec e-beam writer, Apr 3
Igor Todoshchenko, O.V. Lounasmaa Laboratory, Aalto University, Finland, Quantum Diffusion of Vacancies in 4He Crystals, Apr 9
Dimitri Golubev, O.V. Lounasmaa Laboratory, Aalto University, Finland, Parity effect in high temperature superconductors, Apr 10
Karthikeyan S. Kumar, O.V. Lounasmaa Laboratory, Aalto University, Finland,
Population transfer in a superconducting quantum circuit, Apr 17
Bernard Placais, Laboratoire Pierre Agrain, Ecole Normale Superieure, Paris, France,
Electron quantum optics with edge states (guest lecture), Apr 23
Joonas Govenius, O.V. Lounasmaa Laboratory, Aalto University, Finland, Microwave nanobolometer based on proximity Josephson junctions, Apr 24
Bernard Placais, Laboratoire Pierre Agrain, Ecole Normale Superieure, Paris, France,
Electron quantum optics with edge states (guest lecture), Apr 25
Yasuhiro Utsumi, Mie University, Japan, Fluctuation theorem for heat transport
probed by a thermal probe electrode, Apr 29
Ville Maisi, Aalto University, O.V. Lounasmaa Laboratory, Finland, Andreev tunneling and quasiparticle excitations in mesoscopic normal metal – superconductor structures, Apr 30
Teemu Ojanen, O.V. Lounasmaa Laboratory, Aalto University, Finland, Ground state
cooling of mechanical resonator in the unresolved sideband limit, May 8
Matthias Brandt, O.V. Lounasmaa Laboratory, Aalto University, Finland, Controlled
coupling of a SiN membrane to a microwave cavity, Aug 28
Raphael Khan, O.V. Lounasmaa Laboratory, Aalto University, Finland, Effects of
cross-Kerr coupling in a mechanical resonator - cavity system, Sep 11
Ville Kauppila, O.V. Lounasmaa Laboratory, Aalto University, Finland, Theory of
non-equilibrium temperature fluctuations in diffusive conductors, Sep 17
Juha Tuoriniemi, O.V. Lounasmaa Laboratory, Aalto University, Finland, Mixtures
of Bose and Fermi superfluids, Sep 17
Pertti Hakonen, O.V. Lounasmaa Laboratory, Aalto University, Finland, Currentcurrent correlations in graphene and in nanowires with superconducting contacts, Sep
18
Annual Report 2014
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Graham Machin, National Physical Laboratory (NPL), UK, The Euramet metrology
research programme project: Implementing the new Kelvin (InK), Sep 24
Christian Flindt, University of Geneva, Switzerland, Electron waiting times in
mesoscopic transport, Sep 25
Mika Sillanpää, Department of Applied Physics, Aalto University, Finland, Coupling
nanoelectronics to macroscopic quartz resonators, Oct 2
Anna Feshchenko, O.V. Lounasmaa Laboratory, Aalto University, Finland, Realization of a Coulomb gap refrigerator, Oct 16
Xuefeng Song, O.V. Lounasmaa Laboratory, Aalto University, Finland, Introducing
tension and superconducting electrodes to a suspended graphene mechanical resonator,
Oct 23
Ivan Khaymovich, O.V. Lounasmaa Laboratory, Aalto University, Finland, Large
deviation principle, fluctuation relations, and multifractality of wave functions, Oct 30
Alexander Melnikov, Institute for Physics of Microstructures, Nizhny Novgorod,
Russia, Resonant tunneling of fluctuating Cooper pairs, Nov 4
Gordey Lesovik, Landau Institute, Russia, Unitarity of quantum evolution, derivation
of Born rule and repeated measurements problem, Nov 5
Jukka Pekola, O.V. Lounasmaa Laboratory, Aalto University, Finland, Calorimetry
for quantum circuits, Nov 6
Antti Laitinen, O.V. Lounasmaa Laboratory, Aalto University, Finland, 1/f noise in
suspended bilayer graphene, Nov 13
Mathieu Taupin, O.V. Lounasmaa Laboratory, Aalto University, Finland, NormalSuperconductor-Normal device under magnetic field, Nov 20
Mika Oksanen, O.V. Lounasmaa Laboratory, Aalto University, Finland, Graphene
optomechanics at microwave frequencies, Nov 27
Russell Lake, Department of Applied Physics, Aalto University, Finland, Measuring
frequency-dependent impedance of superconductor/normal-metal/superconductor
(SNS) weak links, Dec 4
Karthikeyan S. Kumar, O.V. Lounasmaa Laboratory, Aalto University, Finland,
Modulation effects in a superconducting qubit, Dec 11
BRAIN RESEARCH SEMINARS
Fariba Sharifian, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland, Adaptation Decorrelates Neural Activation Patterns in Visual Cortex, Jan 20
Kristian Donner, Department of Biological and Environmental Sciences, University
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of Helsinki, Finland, Ragnar Granit: background and impact of a Finnish Nobel Prize
winner, Feb 3
Synnöve Carlsson, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland,
The neurobiology of thought: the groundbreaking discoveries of Patricia GoldmanRakic 1937-2003, Feb 17
Lotta Hirvenkari BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland, Natural stimuli in studies of neural basis of social interaction, Mar 3
Siina Pamilo, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland, A correlation-based method for extracting subject-specific components and artifacts from
group-fMRI data, Mar 3
Kia Nobre, University of Oxford, UK, Time for the Fourth Dimension in Attention,
Mar 7
Annika Hulten, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland, Mother Of all Unification Studies - Six big questions about sentence processing, Mar 17
Jukka-Pekka Kauppi, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland,
Data-driven Analysis Methods for Neuroscientists: An Overview of Spectrospatial
Decoding and Inter-Subject Correlation Toolboxes, Mar 17
Miiamaaria Kujala, Department of Equine and Small Animal Medicine, Faculty of
Veterinary Medicine, University of Helsinki, Finland, Eye gaze and neural processing,
Mar 31
Martin Giese, University Clinic Tübingen, Germany, Neural theory for the visual
recognition of goal-directed actions, Apr 9
Andrew Simpson, QMUL Centre for Digital Music / UCL Ear Institute, UK, Selective adaptation to "oddball" sounds by the human auditory system, Apr 14
Eeva Parkkonen, O.V. Lounasmaa Laboratory, Aalto University, Finland, Monitoring
motor-cortex plasticity during stroke recovery using passive movements, Apr 28
Anni Nora, O.V. Lounasmaa Laboratory, Aalto University, Finland, Cortical correlates of learning new phonological forms in adults and children, Apr 28
May 12
Disa Sauter, University of Amsterdam, Netherlands, Disentangling happiness: Evidence for distinct positive emotions from vocal signals, May 12
Anne Mandel, O.V. Lounasmaa Laboratory, Aalto University, Finland, MEG responses to other person’s eye blinks, May 26
Anna Maria Alexandrou, O.V. Lounasmaa Laboratory, Aalto University, Finland,
Exploring naturalistic speech using MEG and peripheral measures, May 26
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Bettina Sorger, Maastricht University, The Netherlands, Exploiting cognitive processing and brain hemodynamics for detecting consciousness in non-responsive patients and motor-independent communication of the paralyzed, Aug 5
Lars Riecke, Maastricht University, The Netherlands, Attention on tonotopy: Taskand stimulus-driven audio-frequency representations in human supratemporal cortex,
Aug 5
Sophie Scott, University College London, UK, The Neuroscience of Laughter, Sep 10
Matti Hämäläinen, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland,
The Quest for the Philosopher's Stone of Human Brain Imaging, Sep 22
Claudia Tesche, The University of New Mexico, US, A MEG Study of Fetal Alcohol
Spectrum Disorder in Adolescents, Oct 9
Christoph Dinh, Technische Universität Ilmenau, Germany, Real-Time MEG Source
Localization using Source Space Clustering, Oct 20
Lorenz Esch, Technische Universität Ilmenau, Germany, MNE Browse Raw Qt: A
Cross Platform Multimodal Data Browser, Oct 20
Hanna Heikkinen, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland,
Spiking neural network simulations for bridging functional imaging data and neuron
level activity, Nov 17
Kaisu Lankinen, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland,
Studying movie-related brain activity with MEG, Nov 17
Synnöve Carlson, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland, Imaging the young brain: top-down control of sensory information processing, Nov 24
Mathilde Ménoret, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland,
Modulation of rolandic beta-band oscillations during motor imagery of joint action,
Dec 15
Sasa Kivisaari, BRU, O.V. Lounasmaa Laboratory, Aalto University, Finland, Processing of meaningful objects in the anteromedial temporal lobe, Dec 15
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SPECIAL ASSIGNMENTS
Tomi Karjalainen, Magnetoencephalography compatible position estimation using
inertial and magnetic sensors. Instructor: Prof. Riitta Hari.
Mikael Kervinen, Frequency tunable superconducting resonator for quantum
circuits. Instructor: Prof. Mika Sillanpää.
Antti Laitinen, Graphene RF-FET as a Detector of Mechanical Vibration. Instructor:
Prof. Pertti Hakonen.
Jori Lemettinen, Gallium nitride thin films for microwave frequency bulk acoustic
resonators. Instructor: Dr. Juha Pirkkalainen.
Elsa Mannila, Influence of magnetic field on the current of a single-electron turnstile.
Instructor: Prof. Jukka Pekola.
Slawomir Simbierowicz, Realizing the coupling of two transmon qubits to a common
coplanar waveguide cavity. Instructor: Prof. Mika Sillanpää.
ACADEMIC DEGREES
BACHELOR THESES
Ilves Jesper, Design and fabrication of a high frequency superconducting microwave
cavity, Instructor and Supervisor: Prof. Mika Sillanpää.
Mannila Elsa, Implementation of data acquisition and preprocessing with a fieldprogrammable gate array, supervisor: Prof. Jukka Pekola.
Prittinen Taneli, He-3 NMR with a SQUID-based equipment, instructor: Doc. Vladimir Eltsov.
Tuominen Riku, Puheenkäsittely luonnollisessa ääniympäristössä: aivotoiminnallinen perusta, supervisor: Prof. Riitta Salmelin, instructor: Dr. Hanna Renvall.
DIPLOMA THESES
Häkkinen Pasi, Single-walled carbon nanotubes as nonlinear mechanical resonators,
supervisor and instructor: Prof. Pertti Hakonen.
Kamppinen Timo, Acoustic resonances in quartz tuning fork container cavity in 4He
gas, supervisor: Prof. Pertti Hakonen, instructor: Doc. Vladimir Eltsov.
Laitinen Antti, Electrical Transport Experiments on Suspended Graphene, supervisor
and instructor: Prof. Pertti Hakonen.
Sulkko Jaakko, Cross-Correlation Measurement of a Nanomechanical Oscillator
Coupled to a Superconducting Cavity, supervisor and instructor: Prof. Mika Sillanpää.
Vepsäläinen Antti, Quantum trajectory simulation of weak measurements with postselection, supervisor: Prof. Jukka Pekola, instructor: Doc. Sorin Paraoanu.
Vesterinen Hannu, Development of frequency response measurement for micromechanical accelerometer, supervisor: Prof. Mika Sillanpää, instructor: Mikko Partanen.
Viisanen Klaara, Measuring temperature relaxation on a small proximized normal
metal island with an RF-NIS thermometer, supervisor: Prof. Jukka Pekola, instructor:
Simone Gasparinetti.
Annual Report 2014
– 99 –
PH.D. DISSERTATIONS
Juha-Matti Pirkkalainen defended his Ph.D. thesis Mechanical Resonators Coupled
to Superconducting Circuits on April 11th, 2014. His opponent was Prof. Eugene Polzik, Niels Bohr Institute, Copenhagen University, Denmark, supervisor and instructor
Prof. Mika Sillanpää.
Ville Maisi defended his Ph.D. thesis Andreev tunneling and quasiparticle excitations
in mesoscopic normal metal - superconductor structures on April 30th, 2014. His opponent was Prof. Hugues Pothier, CEA Saclay, France, supervisor Prof. Jukka Pekola
and instructor Dr. Antti Manninen (MIKES).
Simone Gasparinetti defended his Ph.D. thesis Dissipation at the Nanoscale:
Cooper-pair Pumping and Electron Thermometry on November 18th, 2014. His opponent was Prof. David Haviland, KTH Royal Institute of Technology, Sweden, supervisor and instructor Prof. Jukka Pekola.
Robert Boldt defended his Ph.D. thesis Functional and anatomical brain networks:
Brain networks during naturalistic auditory stimuli, tactile stimuli and rest. Functional network plasticity in early-blind subjects. on December 11th, 2014. His opponent
was Prof. Tianzi Jiang, The Chinese Academy of Sciences, supervisor Prof. Synnöve
Carlson.
Annual Report 2014
– 100 –
TECHNICAL SERVICES
CRYOGENIC LIQUIDS
Jari Isomäki and Joel Salminen
Liquid helium
The total amount of liquid helium purchased was 45 666,4 l and 38 549,8 l were delivered to the users. The losses (boil-off) of the liquid He was 15,6%. The equivalent of
21 485,1 l of liquid He has been collected in He gas recovery system in Nanotalo.
The user distribution is depicted below.
ROTA PICO NEMS BRAIN LT-­‐STM NANO MAGNETOMETER uKI NANOSPIN Figure 30: The distribution of liquid He usage (%) in 2014.
Liquid nitrogen
Significant part of liquid nitrogen was used for compressed nitrogen gas system in
Nanotalo. Total amount of liquid nitrogen purchased was 35 030 kg.
MACHINE SHOP
Jari Isomäki, Markku Korhonen, and Joel Salminen
Our machine shop is part of the Low Temperature Laboratory research infrastructure.
Annual Report 2014
– 101 –
NANO PICO NEMS KVANTTI MOL.MAT. uKI NANOSPIN AMI CENTER BRAIN ROTA BECS SOFTMATTER LT-­‐STM DEMAG Figure 31: The distribution of workshop usage (%) in 2014.
Annual Report 2014
– 102 –
ACTIVITIES OF THE PERSONNEL
AWARDS AND HONORS
Hari Riitta, Commander of the Order of the Lion of Finland
Himberg Tommi, research award "Social eMotions", Koneen säätiö, Helsinki, Finland
Pekola Jukka, Academy Professor, Academy of Finland, 2014 - 2018
Saira Olli-Pentti, Best doctoral dissertation in 2013 award, Aalto University, School
of Science, Espoo, Finland
PERSONNEL WORKING ABROAD
Auranen Toni
•
Neuroscience Center Zurich, Zurich, Switzerland, 23. - 23.9.
Borrelli Massimo
•
International Centre for Theoretical Physics, Trieste, Italy, 9. - 23.9.
Bourguignon Mathieu
•
Department of Clinical Neuroscience (CNS), natMEG, Karolinska Institut,
Stockholm, Sweden, 27. - 28.5.
Carlson Synnöve
•
University of Zurich, Laboratory for Social and Neural Systems Research, Zurich, Switzerland, 22. - 23.9.
Gasparinetti Simone
•
Yale University, New Haven (CT), US, 28. - 31.1.
Hakonen Pertti
•
European Microkelvin Platform, University of Heidelberg, Heidelberg, Germany, 5. - 7.4. and 17. - 20.5.
Hari Riitta
•
University of Lyon, LabEX (Laboratories of Excellence) CORTEX, Lyon,
France, 5. - 6.6.
Henriksson Linda
•
MRC Cognition and Brain Sciences Unit, Cambridge, United Kingdom, 20.11.
- 3.12.
Jousmäki Veikko
•
•
Elekta Oy, Onsite Consultation, National Brain Research Centre, Deemed University, Gurgaon, India, 23. - 26.4. and 20. - 25.5.
Elekta Oy, MEG Introductory Training and System Start at National Taiwan
University, Taipei, taiwan, 2. - 12.10.
Kauppila Ville
•
TUDelft, University, Delft, Netherlands, 1.2. - 30.6.
Annual Report 2014
– 103 –
Khaymovich Ivan
•
•
•
Institute for Physics of Microstructures of the Russian Academy of Sciences
(IPM RAS), Nizhny Novgorod, Russia, 14. - 21.3.
International Centre for Theoretical Physics, Research Center, Trieste, Italy,
14. - 25.4. and 28.9. - 13.10.
University of Tor Vergata, Rome, Italy, 13. - 14.10.
Kujala Jan
•
Lyon Neuroscience Research Center, Lyon, France, 12. - 17.1.
Kumar Manohar
•
Anniversary Workshop on Transport in Nanostructures 10th Capri Spring
School 2014, Capri, Italy, 28.4. - 3.5.
Nora Anni
•
Cold Spring Harbor Laboratory course: Genetics & Neurobiology of Language,
Lloyd Harbor, New York, United States, 28.7. - 3.8.
Nyrhinen Mikko
•
Laboratory for Social and Neural Systems Research (SNS-Lab), University of
Zurich, Zurich, Switzerland, 22. - 23.9.
Pekola Jukka
•
•
•
•
Q-net project meeting, San Sebastian, Spain, 20. - 21.2.
Infernos -review, Brussels, Belgium, 3. - 4.3.
Microsoft collaboration semi-annual meeting, Santa Barbara, USA, 4.11. 8.12.
Kyoto University; Kyoto, Japan, 22. - 29.11.
Peltonen Joonas
•
Royal Holloway, University of London, London, UK, 27.9. - 4.10.
Piitulainen Harri
•
•
•
Laboratory of Engineering of Neuromuscular System and Motor Rehabilitation, Politecnico di Torino, Turin, Italy, 12. - 15.5.
Department of Clinical Neuroscience (CNS), natMEG, Karolinska Institut,
Stockholm, Sweden, 27. - 28.5.
UZ Leuven, Clinical Motion Analysis Laboratory, Leuven, Belgium, 9. 11.12.
Renvall Ville
•
Athinoula A. Martinos Center for Biomedical Imaging, MGH, Charlestown,
USA, 22.4. - 8.5.
Saad Elyana
•
University of Glasgow, Glasgow, Scotland, UK, 24.3. - 24.9.
Annual Report 2014
– 104 –
Salmelin Riitta
•
•
•
•
•
European Commission, 5th Meeting of President's Science and Technology
Advisory Council, Brussels, Belgium, 30. - 31.1.
European Commission, Foresight Workshop "2030 Science, engineering, technology & innovation: what's in it for society?", Brussels, Belgium, 1. - 2.4.
European Commission, 6th Meeting of President's Science and Technology
Advisory Council, Brussels, Belgium, 13. - 14.4.
University of Minneapolis; member of the External Advisory Panel for the
NIH/Human Connectome Project consortium, Minneapolis, MN, USA, 25. 26.4.
European Commission, 7th Meeting of President's Science and Technology
Advisory Council, Brussels, Belgium, 8. - 9.9.
Suvilehto Juulia
•
•
Georgetown University, Laboratory of Integrative Neuroscience and Cognition, NW, Washington D.C., USA, 23.4.
University of Maryland, Laboratory of Cognition and Emotion, College Park,
MD, USA, 24.4.
Todoshchenko Igor
•
Lancaster University, Lancaster, UK, 21. - 30.3.
Virtanen Pauli
•
•
Scuola Normale Superiore, Pisa, Italy, 1. - 7.6.
TU Braunschweig, Braunschweig, Germany, 6. - 10.10.
CONFERENCE PARTICIPATION AND LABORATORY VISITS
Alexandrou Anna Maria
•
poster, Listening to Natural Speech: Effect of stimulus rhtyhmicity and content
on MEG power spectra, 6th Annual Meeting of the Society for the Neurobiology of Language (SNL 2014), Amsterdam, The Netherlands (27. - 29.9.)
Auranen Toni
•
participation, 16th Kuopio Bio-NMR Workshop: From basics to advanced functional MRI, Kuopio, Finland (11. - 12.6.)
Autti Samuli
•
•
•
oral presentation, Dynamics and interactions of magnon BECs, Physics Days
2014, Tampere, Finland (11. - 13.3.)
oral presentation, Dynamics and interaction of magnon Bose-Einstein condensates, 27th International Conference on Low Temperature Physics (LT27),
Buenos Aires, Argentina (6. - 13.8.)
invited talk, Magnon bound states close to surfaces in superfluid 3He-B, International Conference on Ultra Low Temperature Physics (ULT2014), San Carlos de Bariloche, Argentina (14. - 19.8.)
Annual Report 2014
– 105 –
Bona Silvia
•
•
poster, Dissociation between objective and subjective components of visual
short-term memory: the role of memory load and memory content, The 14th European Workshop of Imagery and Cognition (EWIC), Paphos, Cyprus (18. 20.6.)
poster, The role of lateral occipital cortex and occipital face area in symmetry
detection, 37th European Conference on Visual Perception (ECVP 2014), Belgrade, Serbia (24. - 28.8.)
Bourguignon Mathieu
•
•
poster, Partial directed coherence assessment of the corticokinematic coherence, The 20th Annual Meeting of the Organization for Human Brain Mapping
(OHBM 2014), Hamburg, Germany (8. - 12.6.)
oral presentation, Probing action observation with coherence analysis, 19th International Conference on Biomagnetism (BIOMAG 2014), Halifax, Canada
(24. - 28.8.)
Cox Daniel
•
poster, Cooper-pair Splitting Realised in Graphene Quantum Dots, Physics
Days 2014, Tampere, Finland (11. - 13.3.)
Eltsov Vladimir
•
•
invited talk, Kopnin and rotating superfluid 3He, Landau Days 2014, Chernogolovka, Russia (23. - 25.6.)
oral presentation, Energy dissipation in wave turbulence in superfluid 3He-B in
the T->0 limit, 27th International Conference on Low Temperature Physics
(LT27), Buenos-Aires, Argentina (6. - 13.8.)
Faivre Timothé
•
•
•
poster, Josephson junction based thermometer and its application to bolometry, The 25th International Symposium on Space Terahertz
gy, Moscow, Russia (27. - 30.4.)
oral presentation, SiS' bolometry, Q-NET meeeting, San Sebastian, Spain (20. 21.2.)
oral presentation, Temperature fluctuations as the thermodynamic limit of bolometers and single photon detectors, Q-NET final workshop, Pisa, Italy (9. 11.12.)
Feshchenko Anna
•
•
•
•
poster, Coulomb blockade thermometry towards low temperatures, Physics
Days 2014, Tampere, Finland (11. - 13.3.)
poster, Experimental realization of a Coulomb gap refrigerator; NIS thermometry down to 4 mK, Advanced Research Workshop Fundamentals of Electronic
Nanosystems (NanoPeter 2014), Saint-Petersburg, Russia (21. - 29.6.)
poster, Experimental realization of a Coulomb gap refrigerator, 27th International Conference on Low Temperature Physics (LT27), Buenos Aires, Argentina (6. - 13.8.)
oral presentation, Electron thermometry and cooling, Q-NET meeting, Pisa, Italy (9. - 11.12.)
Annual Report 2014
– 106 –
Forss Nina
•
•
•
participation, 30th International Congress of Clinical Neurophysiology (ICCN),
Berlin, Germany (20. - 23.3.)
invited talk, MEG and stroke recovery, 19th International Conference on Biomagnetism (BIOMAG 2014), Halifax, Canada (24. - 28.8.)
invited talk, Motor cortex oscillations and stroke recovery, BIOMAG 2014,
Halifax, Canada (24. - 28.8.)
Gasparinetti Simone
•
poster, Real-time temperature detection at the nanoscale with a radiofrequency
NIS thermometer, 27th International Conference on Low Temperature Physics
(LT27), Buenos Aires, Argentina (6.8. - 13.10.)
Günes Minna
•
participation, Graphene Flagship workshop for the national press officers,
Gothenburg, Sweden (25.6.)
Hakonen Pertti
•
•
•
•
•
•
•
•
•
•
invited talk, Recent graphene work at O.V. Lounasmaa Laboratory, Kick-off
meeting of iQUOEMS, Camerino, Italy (10. - 11.1.)
oral presentation, Recent graphene work in Helsinki, Kick-off meeting of Graphene Flagship Work Package 7, Amsterdam, The Netherlands (14.1.)
participation, Preparation of a new Microkelvin proposal in Horizon 2020,
Heidelberg, Germany (15. - 17.1.)
invited comment, Summary on discussion session: Comparision of graphene
and carbon nanotube sensors, Graphene Connect: Sensors, Gothenburg, Sweden (23. - 24.6.)
oral presentation, Graphene optomechanics realized at microwave frequencies,
Graphene Week 2014, Gothenburg, Sweden (23. - 27.6.)
oral presentation, Cooper Pair Splitting Realized in Graphene Quantum Dots,
27th International Conference on Low Temperature Physics (LT27), Buenos
Aires, Argentina (6. - 13.8.)
oral presentation, Graphene Optomechanics realized at Microwave Frequencies, LT27, Buenos Aires, Argentina (6. - 13.8.)
invited talk, Suspended carbon nanotube resonators at ultra low temperatures,
International Conference on Ultra Low Temperature Physics (ULT2014), Bariloche, Argentina (15. - 19.8.)
invited talk, Current-current correlations in graphene and in nanowires with
superconducting contacts, Superconducting Nanocircuits 2014 (SNC2014),
Maratea, Italy (7. - 12.9.)
invited plenary talk, Electrical and mechanical resonance modes in suspended
graphene systems, "Two Dimensional Nanostructures", 1st Erwin Schrödinger
Symposium 2014, Vienna, Austria (26. - 28.11.)
Hari Riitta
•
invited talk, (Special lecture:) Brain imaging of social interaction, 30th International Congress on Clinical Neurophysiology (ICCN), Berlin, Germany (20. 23.3.)
Annual Report 2014
– 107 –
•
•
•
•
•
•
•
•
invited talk, We move, sense, and feel together, Dynamics of Active Perception: An Interdisciplinary Symposium on Perception and the Mind-Body Problem; Helsinki Collegium for Advanced Studies, Helsinki, Finland (15. - 16.5.)
invited talk, Taide ja aivot, Terveyttä taiteesta -seminaari (Duodecim),
Savonlinna, Finland (21.7.)
invited plenary talk, (keynote) Brain imaging of social interaction: why and
how, 19th International Conference on Biomagnetism (BIOMAG 2014), Halifax, Canada (24. - 28.8.)
invited talk, Movement and social interacction — indispensable ingredients of
the human mind, Perception and the Mind– from Chemistry to Emotions, Helsinki, Finland (15. - 16.9.)
lecture, Time in human brain function, Frontiers in Cognitive Neuroscience
2014 (Karolinska Institute), Stockholm, Sweden (17.9.)
invited talk, Aivotutkijan käsitys mielestä, Toinen aivot ja mieli, käsitteet ja
kieli -symposium, Helsinki, Finland (13. - 14.10.)
oral presentation, Member (1 of 4) of Panel on The impact of science on human
health, Aalto Academic Summit, Espoo, Finland (18.11.)
invited talk, Understanding others: A neuroscientist’s perspective, Helsinki
Lectures on Intersubjectivity (University of Helsinki), Helsinki, Finland (5.12.)
Heikkinen Hanna
•
•
poster, Bridging spatial spread of fMRI and neural responses in a recurrent
network model of the primary visual cortex, Bernstein Conference 2014, Göttingen, Germany (1. - 5.9.)
poster, Bridging spatial spread of fMRI and neural responses in a spiking network model of the primary visual cortex, 3rd BRAHE symposium, Helsinki,
Finland (22.10.)
Heikkinen Petri
•
•
•
•
•
•
poster, Microkelvin Thermometry with Magnon BEC and Applications to Studies of AB Interface in Superfluid 3He, Physics Days 2014, Tampere, Finland
(11. - 13.3.)
poster, Magnetic relaxation and gravity waves on the free surface of superfluid
3
He-B, 27th International Conference on Low Temperature Physics (LT27),
Buenos Aires, Argentina (6. - 13.8.)
poster, Magnetic relaxation on vortices in 3He-B in the zero temperature limit,
LT27, Buenos Aires, Argentina (6. - 13.8.)
oral presentation, Magnon BEC at the free surface of topological superfluid
3
He-B, International Conference on Ultra Low Temperature Physics
(ULT2014), Bariloche, Argentina (14. - 19.8.)
oral presentation, Microkelvin thermometry in superfluid 3He-B with BoseEinstein condensates of magnons, ULT2014, Bariloche, Argentina (14. - 19.8.)
poster, Coherent excited states in a magnon trap in 3He-B, ULT2014, Bariloche, Argentina (14. - 19.8.)
Henriksson Linda
•
•
participation, Aivot ja mieli, käsitteet ja kieli symposium, Helsinki, Finland
(13. - 14.10.)
participation, Brain Imaging of Social Interaction: Why and How? (poster) by
Annual Report 2014
– 108 –
Riitta Hari, Lauri Parkkonen and Linda Henriksson, Human Brain Project
(HBP) Summit 2014, Heidelberg, Germany (28.9. - 1.10.)
Hietala Niklas
•
poster, Interplay between neighboring superfluid vortices, 27th International
Conference on Low Temperature Physics (LT27), Buenos Aires, Argentina (6.
- 13.8.)
Himberg Tommi
•
•
•
•
oral presentation, Effect of Tempo and Vision on Interpersonal Coordination of
Time, 13th International Conference on Music Perception and Cognition and 5th
Confernce for the Asia-Pacific Society for Cognitive Sciences of Music
(ICMPC-APSCOM 2014), Seoul, South Korea (4. - 8.8.)
oral presentation, Interactionism and Music: Measuring Entrainment and Influence in Dyads and Groups, ICMPC-APSCOM 2014, Seoul, South Korea (4.
- 8.8.)
poster, Improvisation and Change in Videos of 1-to-1 Music Therapy Sessions
With Children With Autism Spectrum Disorders, ICMPC-APSCOM 2014,
Seoul, South Korea (4. - 8.8.)
poster, Entrainment of speech rhythms in a dyadic story-telling task, Society
for Neuroscience Annual Meeting Neuroscience 2014, Washington, DC, US
(15. - 19.11.)
Hultén Annika
•
•
•
invited talk, Linking Names to Meanings to Grammar, Aivotutkimuskeskuksen
seminaari, Jyväskylä, Finland (27.3.)
poster, Lukevat aivot, AIVOJEN SALAT AUKEAVAT Suomen aivotutkimusseura 40 v, Helsinki, Finland (14.10.)
oral presentation, Effects of sentence progression in event-related and rhythmic
neural activity measured with MEG, 6th Annual Meeting of the Society for the
Neurobiology of Language (SNL 2014), Amsterdam, The Netherlands (27. 29.8.)
Hytönen Kaisa
•
•
invited talk, Kuinka ympäristö vaikuttaa päätöksiimme?, Mainonnan valta seminaari, Helsinki, (30.1.)
oral presentation, Do people break even or learn from experience?, 2014 NeuroPsychoEconomics Conference, Munich, Germany (29. - 30.5.)
Hänninen Risto
•
•
•
invited talk, Quantised vortex reconnection, ESF Workshop - Reconnection
Events in Classical, Quantum and Magnetized Fluids, Glasgow, United Kingdom (16. - 18.6.)
oral presentation, Dissipation from Reconnecting Vortex Rings, 27th International Conference on Low Temperature Physics (LT27), Buenos Aires, Argentina (6. - 13.8.)
poster, Quantum turbulence in a pipe: difference between pure superflow and
thermal counterflow, LT27, Buenos Aires, Argentina (6. - 13.8.)
Annual Report 2014
– 109 –
Illman Mia
•
participation, 30th International Congress of Clinical Neurophysiology (ICCN),
Berlin, Germany (20. - 23.4.)
Jousmäki Veikko
•
•
•
poster, Impact of experiment duration on the accuracy of functional mapping
using corticokinematic coherence, 19th International Conference on Biomagnetism (BIOMAG 2014), Halifax, Canada (24. - 28.8.)
poster, Magnetoencephalography benchmarking experiments: high- vs low-TC
squids, BIOMAG 2014, Halifax, Canada (24. - 28.8.)
poster, Movement-related evoked fields using triggers from accelerometer signals, BIOMAG 2014, Halifax, Canada (24. - 28.8.)
Kaikkonen Jukka-Pekka
•
•
poster, Demonstration of sub-millikelvin refrigeration in cryogen-free system,
Physics Days 2014, Tampere, Finland (11. - 13.3.)
poster, Single-walled cabron nanotube mechanical resonators at millikelvin
temperatures, 27th International Conference on Low Temperature Physics
(LT27), Buenos Aires, Argentina (6. - 13.8.)
Khaymovich Ivan
•
•
•
•
oral presentation, Phase transitions in ferromagnetic superconductors with
domain structure, 18th International symposium “Nanophysics & Nanoelectronics”, Nizhny Novgorod, Russia (10. - 14.3.)
oral presentation, Multiple Vortex Cores in 2D Electronic Systems with Proximity Induced Superconductivity, 4th International Conference on Superconductivity and Magnetism (ICSM 2014), Antalya, Turkey (26.4. - 2.5.)
invited talk, Vortex core states within Coulomb blockade regime, Landau Days
2014, Chernogolovka, Moscow district, Russia (23. - 25.6.)
oral presentation, Non-equilibrium fluctuation relations: Bochkov-Kuzovlev
(BKE) vs Jarzynski (JE) equality, Infernos meeting, Barcelona, Spain (7. 8.10.)
Koski Jonne
•
poster, Thermodynamics in a single electron box: Fluctuation relations and
Szilard engine, Advanced Research Workshop Fundamentals of Electronic
Nanosystems (NanoPeter 2014), St. Petersburg, Russia (21. - 27.6.)
Kujala Jan
•
participation, The 20th Annual Meeting of the Organization for Human Brain
Mapping (OHBM 2014), Hamburg, Germany (8. - 12.6.)
Kumar Manohar
•
oral presentation, Shot noise and magnetism of Pt atomic chains: Accumulation
of points at the boundary, Anniversary Workshop on Transport in Nanostructures 10th Capri Spring School 2014, Capri, Italy (28.4. - 3.5.)
Laitinen Antti
•
oral presentation, Ripple-induced electron-phonon supercollisions in graphene,
Annual Report 2014
– 110 –
•
•
Physics Days 2014, Tampere, Finland (11. - 13.3.)
participation, QDev/NBIA Summer School 2014 on Quantum Effects in LowDimensional Systems, Copenhagen, Denmark (29.6. - 5.7.)
oral presentation, 1/f noise in suspended bilayer graphene, 2nd Graphene Flagship Work Package meeting, Delft, Netherlands (13. - 14.10.)
Liljeström Mia
•
•
•
poster, A combined MEG-fMRI spatiotemporal account of semantic vs. perceptual processing of written words, The 20th Annual Meeting of the Organization
for Human Brain Mapping (OHBM 2014), Hamburg, Germany (8. - 12.6.)
poster, Task-related modulations in large-scale cortical networks underlying
language production: a combined fMRI and MEG study, 6th Annual Meeting of
the Society for the Neurobiology of Language (SNL 2014), Amsterdam, the
Netherlands (27. - 29.8.)
poster, A combined MEG-fMRI spatiotemporal account of semantic vs. perceptual processing of written words, 3rd BRAHE Symposium, Helsinki, Finland
(22.10.)
Lindh-Knuutila Tiina
•
invited comment, Sanojen merkityksen jäljillä, Digitaalisten tekstien tuottaminen ja jatkojalostus, Mikkeli, Finland (3.6.)
Maisi Ville
•
•
•
poster, Andreev tunneling in NIS junctions and SINIS turnstiles, 27th International Conference on Low Temperature Physics (LT27), Buenos Aires, Argentina (6. - 13.8.)
poster, Towards circuit QED with semiconductor single-electron charge qubits,
LT27, Buenos Aires, Argentina (6. - 13.8.)
poster, Quasiparticle excitations in SINIS and NISIN turnstiles, LT27, Buenos
Aires, Argentina (6. - 13.8.)
Mandel Anne
•
poster, Brain responses to other person's eye blinks are related to the empathy
of the viewer, Social Brain 2014, Copenhagen, Denmark (5. - 8.10.)
Ménoret Mathilde
•
•
oral presentation, Modulation of rolandic beta-band oscillations during joint
action, Society for Neuroscience Annual Meeting Neuroscience 2014, Washington, DC, USA (15. - 19.11.)
poster, Motor representation during joint actions: Insights from Single & Dual-EEG analyses, Perspectives and future directions in social neuroscience
(HBM 2014), Annual Meeting Satellite, Marburg, Germany (4. - 6.6.)
Meschke Matthias
•
•
oral presentation, Uncertainty components and traceability of coulomb blockade thermommetry, 27th International Conference on Low Temperature Physics
(LT27), Buenos Aires, Argentina (25.8.)
oral presentation, SQUIPT with enhanced responsitivity, LT27, Buenos Aires,
Argentina (25.8.)
Annual Report 2014
– 111 –
•
participation, Q-NET workshop 2014, Pisa, Italy (10. - 11.12.)
Nyrhinen Mikko
•
invited talk, Aalto TMS, TMS-fMRI Workshop 2014, Espoo, Finland (30.11.)
Mäkinen Jere
•
poster, Energy dissipation and librating motion of superfluid 3He-B in the T →
0 limit, Physics days 2014, Tampere, Finland (11. - 13.3.)
Najafi Jabdaraghi
•
poster, non-hysteretic superconducting quantum interference proximity transistor with enhanced responsivity, Physics Days 2014, Tampere, Finland (11. 13.3.)
Nora Anni
•
•
•
•
poster, Auditory and articulatory coding along the dorsal stream when accessing newly learned word forms, The 20th Annual Meeting of the Organization
for Human Brain Mapping (OHBM 2014), Hamburg, Germany (8. - 12.6.)
oral presentation, Cortical correlates of learning foreign language word forms
and phonotactics in adults and children, Annual Meeting of the Doctoral program Brain&Mind, Aavaranta, Kirkkonummi, Finland (11. - 12.9.)
poster, Children learn foreign phonotactics overnight, Brain Research at Aalto
University and University of Helsinki (BRAHE) meeting, Helsinki, Finland
(22.9.)
lecture, Kieli ja aivot – Kielen aivoperustan tutkimus Aivotutkimusyksikössä,
Aivokummien teemailtapäivä, Espoo, Finland (31.10.)
Ojanen Teemu
•
•
•
•
•
oral presentation, Majorana states in Shiba chains and ladders, APS march
meeting 2013, Denver, USA (3. - 7.3.)
oral presentation, Manipulation of topological phases in Shiba chains by supercurrent, New Trends in Topological Insulators (NTTI) 2014, Berlin, Germany (7. - 10.7.)
poster, Controlling topological phases by supercurrent in Shiba chains, Nordita Conference on Quantum Engineering of states and devices 2014, Stockholm,
Sweden (18.
invited talk, Topological superconductivity in magnetic Shiba structures, Topological and Dirac matter: from modeling to imaging, Bordeaux, France (12. 14.11.)
invited talk, Topological superconductivity in Shiba lattices, Oslo workshop in
topological phenomenon in low-dimensional systems, Oslo, Norway (9. 11.12.)
Oksanen Mika
•
poster, Electron-phonon coupling in suspended graphene: supercollisions by
ripples, Graphene week 2014, Gothenburg, Sweden (23. - 27.6.)
Annual Report 2014
– 112 –
Paraoanu Sorin
•
•
•
•
•
•
•
•
invited comment, Presentation as panel member, Physics of Information
(FQXi 2014), Vieques, Puerto Rico (5. - 10.1.)
oral presentation, Simulation of motional averaging using a superconducting
circuit, Discrete and Analog Quantum Simulators, Bad Honnef, Germany (10. 12.2.)
invited talk, Circuit QED as an experimental platform for analog quantum relativistic effects, Weizmann COST 2014 - Fundamental problems in quantum
physics, Rehovot, Israel (23. - 27.3.)
invited talk, Simulation of motional averaging with a superconducting circuit,
guest lecture at Technion - Israel Instutute for Technology, Haifa, Israel (27.3.)
invited talk, Simulation of motional averaging with a superconducting circuit,
seminar at Racah Institute of Physics, Univ. of Jerusalem, Jerusalem, Israel
(25.3.)
invited talk, Generation of pairs of entangled photons by the dynamical Casimir effect in a SQUID array, Casimir Physics, Les Houches, France (30.3. 4.4.)
oral presentation, Periodic modulation of the transition frequency in a superconducting qubit, Advanced many-body and statistical methods in mesoscopic
physics II, Brasov, Romania (1. - 5.9.)
invited talk, State Control an Decoherence in Circuit QED Systems, Workshop
on Entanglement, Decoherence, and Quantum Control (EDQC2014), Buffalo,
U.S.A. (22. - 24.10.)
Parkkonen Eeva
•
•
poster, Modulation of the 20-Hz rhythm to passive movement and tactile stimulation, 30th International Congress of Clinical Neurophysiology (ICCN), Berlin, Germany (19. - 23.3.)
poster, Dynamics of ~20-Hz motor-cortex oscillations in stroke recovery, 19th
International Conference on Biomagnetism (BIOMAG 2014), Halifax, Canada
(24. - 28.8.)
Pekola Jukka
•
•
•
•
•
•
•
invited talk, Energy fluctuations and Maxwell’s demon in nano- scale systems,
Nanoscience Colloquium, Lund, Sweden (10.4.)
invited talk, Energy fluctuations and Maxwell's demon in nano-scale systems,
Horizon2020 FET Workshop for Young Researchers, Gothenburg, Sweden (6.
- 7.5.)
invited talk, Energy fluctuations and Maxwell's demon in electronic circuits,
Heidelberg University Physics Colloquium, Heidelberg, Germany (23.5.)
invited talk, Under theme “Quantum Technologies at ultra-low temperatures”,
Quantum Technology Centre Launch, Lancaster, UK (28. - 29.5.)
invited talk, Energy fluctuations and Maxwells demon in a single-electron circuit, 9th Advanced Research Workshop NanoPeter 2014, Saint Petersburg,
Russia (22. - 26.6.)
invited talk, Kopnin and nanophysics experiments, Landau Days 2014, Chernogolovka, Russia (23. - 25.6.)
participation, Condensed Matter Physics Seminar, Lancaster, UK (30.6. - 1.7.)
Annual Report 2014
– 113 –
•
•
•
•
•
•
•
•
•
•
invited talk, Dissipation in electronic circuits at low temperatures: fluctuation
relations and Maxwell demon, 27th International Conference on Low Temperature Physics (LT27), Buenos Aires, Argentina (6. - 13.8.)
invited talk, Maxwell demon in an electronic circuit, QDev Seminar, Copenhagen, Denmark (13. - 16.8.)
invited plenary talk, Energy fluctuations and Maxwell's demon in an electric
circuit, Condensed Matter in Paris 2014, Paris, France (24. - 29.8.)
invited talk, Counting statistics of Andreev tunneling, Superconducting
Nanocircuits 2014 (SNC2014), Maratea, Italy (7. - 9.9.)
invited talk, Thermal effects at nano-scale, European School On Nanosciences
& Nanotechnologies ESONN 2014, Grenoble, France (11. - 12.9.)
invited talk, Maxwell's demon in an electronic circuit, Quantum Physics TCQP Colloquim, Turku, Finland (22.9.)
invited talk, Quantum thermodynamics in superconducting circuits, Advanced
Workshop on Landau-Zener Interferometry and Quantum Control in Condensed Matter, Izmir, Turkey (29.9. - 3.10.)
invited talk, Maxwell's demon and calorimetric measurement of dissipation in
a quantum circuit, 2014 Workshop of the Collaborative Research Center of the
German Science Foundation in Control of Quantum Correlations in Tailored
Matter CO.CO.MAT, Günzburg, Germany (6. - 8.10.)
invited talk, Non-equilibrium, fluctuations and information in mesoscopic electric circuits, The 27th Workshop on Mesoscopic and Nanoscale Systems, Seoul,
Korea (20. - 22.11.)
invited talk, Towards quantum thermodynamics in electric circuits, Mathematical Physics Seminar, Helsinki, Finland (17.12.)
Piitulainen Harri
•
•
poster, Phasic stabilization of the human primary motor cortex by visual and
auditory stimuli, , The 20th Annual Meeting of the Organization for Human
Brain Mapping (OHBM 2014), Hamburg, Germany (8. - 12.7.)
oral presentation, Exploring coupling between cortical activity and motor actions with corticokinematic coherence, 19th International Conference on Biomagnetism (BIOMAG 2014), Halifax, Canada (24. - 28.8.)
Pirkkalainen Juha-Matti
•
poster, Optomechanics with Josephson junction cavities, Mechanical Systems
in the Quantum Regime, Gordon Research Conference, Ventura (CA), USA (9.
- 14.3.)
Rajamäki Riikka
•
poster, Changes in corticomuscular coherence after acute stroke, 3rd BRAHE
Symposium, Helsinki, Finland (22.10.)
Renvall Hanna
•
invited talk, Attention to speech sounds within auditory scenes modifies temporal cortical activity, 6th Annual Meeting of the Society for the Neurobiology
of Language (SNL 2014), Amsterdam, The Netherlands (27. - 29.8.)
Annual Report 2014
– 114 –
Renvall Ville
•
•
poster, Fast variable inversion-recovery time EPI for anatomical reference and
quantitative T1 mapping, Joint Annual Meeting of The International Society
for Magnetic Resonance in Medicine and The European Society for Magnetic
Resonance in Medicine and Biology (ISMRM-ESMRMB 2014), Milan, Italy
(10. - 16.5.)
poster, Multi-contrast inversion-recovery EPI (MI-EPI) functional MRI at 7 T,
ISMRM-ESMRMB 2014, Milan, Italy (10. - 16.5.)
Saira Olli-Pentti
•
poster, Radio-frequency electron thermometry at the nanoscale down to 100
mK, 9th Advanced Research Workshop NanoPeter 2014, St. Petersburg, Russia
(22. - 27.6.)
Salmelin Riitta
•
•
•
•
•
•
•
•
invited talk, Neuroimaging of human cognition, Visit of GE Healthcare to Aalto University, Espoo, Finland (24.1.)
invited talk, Human brain imaging: from big data to really big data, Dean's
Circle, Aalto University School of Science, Espoo, Finland (13.2.)
invited talk, Language processing: insights from MEG and fMRI, 30th International Congress of Clinical Neurophysiology (ICCN2014), Berlin, Germany
(20. - 23.3.)
participation, The 20th Annual Meeting of the Organization for Human Brain
Mapping (OHBM 2014), Hamburg, Germany (8. - 12.6.)
participation, 6th Annual Meeting of the Society for the Neurobiology of Language (SNL2014), Amsterdam, The Netherlands (27. - 30.8.)
participation, The Future of Europe is Science, Lisbon, Portugal (6. - 7.10.)
invited talk, National Roadmap for Research Infrastructures, 3rd BRAHE
Symposium, Helsinki, Finland (22.10.)
invited talk, What you measure is what you get — Imaging views to language
processing, Neuroscience Finland 2014, Helsinki, Finland (9.12.)
Seppälä Kerttu
•
participation, Neurodynamics of Language and Music symposium, Helsinki, ,
Finland (12. - 13.6.)
Sharifian Fariba
•
poster, Adaptation decorrelates neural activation patterns in visual cortex, 37th
European Conference on Visual Perception (ECVP), Belgrade, Serbia (24. 28.8.)
Sillanpää Mika
•
•
invited talk, Optomechanics at microwave frequencies: mechanical resonators
coupled to microwave cavities and superconducting qubits, 46th Confernece of
the European Group on Atomic Systems (EGAS46), Lille, France (1. - 4.7.)
invited talk, Optomechanics at microwave frequencies: mechanical resonators
coupled to microwave cavities and superconducting qubits, ESF Workshop:
Quantum Technologies - Hybrid-Emitter Solid State Systems, Strasbourg,
France (21. - 24.9.)
Annual Report 2014
– 115 –
Suvilehto Juulia
•
poster, U can't touch this: Spatial topography of social touching, Society for
Affective Science, 2014 Inaugural Conference, Bethesda, Washington DC,
USA (24. - 26.4.)
Tan Zhengbing
•
oral presentation, Cooper pair splitting realised in graphene quantum dots,
Graphene Week 2014, Gothenburg, Sweden (23. - 27.6.)
Todoshchenko Igor
•
•
•
•
oral presentation, Quantum diffusion of vacancies in 4He crystals, 27th International Conference on Low Temperature Physics (LT27), Buenos Aires, Argentina (6. - 13.8.)
poster, Sub-millikelvin refrigeration on a dry demagnetization cryostat, LT27,
Buenos Aires, Argentina (6. - 13.8.)
oral presentation, Stress-induced vacancies in 4He crystals, International Conference on Ultra Low Temperature Physics (ULT2014), Bariloche, Argentina
(15. - 19.8.)
oral presentation, Superfluid 3He in a dry demagnetization cryostat, ULT2014,
Bariloche, Argentina (15. - 19.8.)
Tsai Kevin
•
poster, Ultrafast Inverse Imaging of the Human Face Recognition System, The
20th Annual Meeting of the Organization for Human Brain Mapping (OHBM
2014), Hamburg, Germany (8. - 12.6.)
Tuoriniemi Juha
•
poster, Surface waves on superfluids 3He and 4He, 27th International Conference on Low Temperature Physics (LT27), Buenos Aires, Argentina (6. - 13.8.)
Vepsäläinen Antti
•
poster, Simulation of weak quantum measurement with post-selection in cavity
quantum electrodynamics, Physics Days 2014, Tampere, Finland (11. - 13.3.)
Virtanen Pauli
•
poster, Microwave spectroscopy of Josephson junctions in 1D topological superconductors, Nordita Conference on Quantum Engineering of states and devices 2014, Stockholm, Sweden (18. - 23.8.)
Volovik Grigori
•
•
•
•
participation, Editorial Board meeting of the journal JETP Letters, Moscow,
Russia (6.2.)
lecture, Topology in physics, International Winter School for Theoretical Physics, Ekaterinburg, Russia (23.2. - 1.3.)
lecture, Topology in momentum space: From particle physics to roomtemperature superconductivity, lecture at Russian Quantum Center, Skolkovo,
Russia (26.3.)
invited talk, Flat band and room-temperature superconductivity, seminar at
Landau Institute, Chernogolovka, Russia (28.3.)
Annual Report 2014
– 116 –
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
invited talk, Flat bands & room Tc superconductivity, seminar at Lebedev
Physical Institute, Moscow, Russia (22.5.)
lecture, Gapless topological matter: From Standard Model of particle physics
to room-temperature superconductivity, Summer School: Topological states of
matter, Gothenburg, Sweden (8. - 13.6.)
invited talk, Higgs Bosons in Particle Physics & in Topological Superfluid
3
He, Symposium Topological States of Matter, Gothenburg, Sweden (10. 11.6.)
invited talk, From Standard Model of particle physics to room-temperature superconductivity, Nobel Symposium 156: New Forms of Matter - Topological
Insulators and Superconductors, Stockholm, Sweden (12. - 15.6.)
invited talk, Kopnin force and chiral anomaly, Landau Days 2014, Chernogolovka, Russia (22. - 25.6.)
invited talk, Kopnin in Physics, Landau Days 2014, Chernogolovka, Russia
(22. - 25.6.)
invited talk, Towards room-temperature flat-band superconductivity, Landau
Days 2014, Chernogolovka, Russia (22. - 25.6.)
participation, meeting of dissertation council of Landau Institute, PhD defence
by Tarnopolsky G.M., Chernogolovka, Russia (27.6.)
invited talk, From Standard Model of particle physics to room-temperature superconductivity, colloquium at Jyvaskyla University, Jyvaskyla, Finland
(10.10.)
participation, Editorial Board meeting of the journal JETP Letters, Moscow,
Russia (18.9.)
participation, editorial Board meeting of the journal JETP Letters, Moscow,
Russia (23.10.)
participation, Editorial Board meeting of the journal JETP Letters, Moscow,
Russia (27.11.)
invited plenary talk, Topology in physics, International Conference on Topological Quantum Phenomena (TQP2014), Kyoto, Japan (16. - 20.12.)
participation, meeting of the Committee of Topological Quantum Phenomena
project, Kyoto, Japan (20.12.)
participation, Editorial Board meeting of the journal JETP Letters, Moscow,
Russia (25.12.)
participation, meeting of dissertation council of Landau Institute, defence of
PhD by A.A. Gelash, Chernogolovka, Russia (26.12.)
EXPERTISE AND REFEREE ASSIGNMENTS
Alexandrou Anna Maria
Chairman of the session:
• Language, Music and Rehabilitation session, Brain & Mind Annual Symposium
2014, Kirkonummi, Finland, 11. - 12.9.
Forss Nina
Member of Awards Committee:
Annual Report 2014
– 117 –
• Biomag 2014, Halifax, Canada, 24. - 28.8.
Hakonen Pertti
Membership in distinguished societies:
• Finnish Academy of Sciences and Letters
• Fellow member, American Physical Society
• Academia Europaea
Position of trust in scientific organizations:
• Review panel of the FP7 FET-Open -project SE2ND: Source of Entangled Electrons in Nano Devices 2011 – 2014
• Panel member, Vetenskaprådet, Applied physics, NT15, Stockholm, Sweden, 14. 16.9.
• Director of Low Temperature Laboratory infrastructure
• Expert member, Otaniemi Research Infrastruture for Micro and Nanotechnologies
(OtaNano) steering group, Espoo, Finland
Chairman of the conference or organising committee:
• 5th Graphene and 2D Materials Satellite Symposium (GSS14) in NT14, Los Angeles, USA, 2. - 6.6.
Chairman of the session:
• Morning session I: graphene applications, Graphene Week 2014, Gothenburg,
Sweden, 23. - 27.6.
• Circuit quantum electrodynamics session, Superconducting Nanocircuits – 2014,
Maratea, Italy, 7. - 12.9.
Opponent:
• Ben Schneider, Suspended Carbon Nanotubes Coupled to Superconducting Circuits, Delft University of Technology, Delft, The Netherlands, 3.7.
Pre-examiner of a thesis:
• Ben Schneider, Suspended Carbon Nanotubes Coupled to Superconducting Circuits, Delft University of Technology, Delft, The Netherlands, 25.5.
Referee:
• Nature
• Physical Review Letters
Interview:
• Helium on jalo kaasu, Kemia-Kemi, Magazine, Finland, 20.3.
Hari Riitta
Membership in distinguished societies:
•
•
•
•
National Academy of Sciences of the USA
Finnish Academy of Technical Sciences
Finnish Academy of Sciences and Letters
Academia Europaea
Position of trust in scientific organizations:
Annual Report 2014
– 118 –
• Member of International Scientific Advisory Board, Karolinska Institute, NeuroSTRAT Program in Neuroscience, Stockholm, Sweden, 1.9.2012 - 31.12.2016
• Member of International Scientific Advisory Board, Karolinska Institute, NatMEG
- The Swedish National Facility for Magnetoencephalography, Stockholm, Sweden, 1.10.2013 - 31.12.2014
• Millennium Prize — Member of the International Selection Committee, Technology Academy Finland
• Chair of a 10-member International Scientific Advisory Board, LabEX (Laboratories of Excellence) CORTEX, Lyon, France, 1.5. - 31.12.
Member of the organising committee (member of International Scientifc Advisory
Board):
• 30th International Congress of Clinical Neurophysiology (ICCN) of the IFCN, Berlin, Germany, 20. - 23.3.
Statement for the appointment of a professor:
• Chaire de recherche du Canada (niveau 2), University of Montreal, Montreal, Canada, 28.4.
• Full Professor, McGill University, Faculty of Medicine, Montreal, Canada, 30.5.
Member of the editorial board:
•
Cerebral Cortex
Editor of scientific journal:
• PNAS (Member editor)
Referee:
• PLOS ONE
• PNAS
• Psychophysiology
Interview:
• Johtajien palkoista, Kauppalehti, Magazine, Helsinki, Finland, 10.2.
• Kahden ihmisen neurotiede selvittää ihmisen sosiaalisuutta, Academy of Finland,
Electronic publication, Finland, 6.3.
Heikkinen Hanna
Referee:
• Frontiers in Integrative Neuroscience
• Human Brain Mapping
Interview:
• Mitä aivokuvat kertovat tunteistamme?, Yle, TV, Helsinki, Finland, 1.12.
Heikkinen Petri
Interview:
• Helium on jalo kaasu, Kemia-Kemi, Magazine, Finland, 20.3.
Henriksson Linda
Member of scientific associations:
Annual Report 2014
– 119 –
• Academy Club for Young Scientists of the Finnish Academy of Science and Letters
Referee:
• Neurorehabilitation & Neural Repair
• PLOS ONE
• Visual Cognition
Himberg Tommi
Referee:
•
•
•
•
•
Frontiers in Human Neuroscience
Frontiers in Psychology - Auditory Cognitive Neuroscience
Musicae Scientiae
Philosophical Transactions of the Royal Society B
Psychology of Music
Hulten Annika
Opponent:
• Irina Simanova, In search of conceptual representations in the brain: Towards
mind-reading, Radboud Universiteit Nijmegen, Nijmegen, The Netherlands, 12.5.
Referee:
• Journal of Cognitive Neuroscience
• Journal of Neuroscience
Interview:
• Radiohuset, YLE, Radio, Helsinki, Finland, 13.3.
Hytönen Kaisa
Referee:
• Social Neuroscience
Interview:
• The Bull That Got Away; How investors can keep their emotions from dominating
decision-making, The Wall Street Journal, Newspaper, New York, United States,
15.3.
Hänninen Risto
Chairman of the session:
• Morning session I: Experimental systems, ESF Workshop - Reconnection Events
in Classical, Quantum and Magnetized Fluids, University of Glasgow, United
Kingdom, 16. - 18.6.
Referee:
•
•
•
•
Journal of Low Temperature Physics
Physical Review B
Physical Review Letters
Proceedings of the Royal Society A
Annual Report 2014
– 120 –
Jousmäki Veikko
Position of trust in scientific organizations:
• Member of International Scientific Advisory Board, Karolinska Institute, NatMEG
- The Swedish National Facility for Magnetoencephalography, Stockholm, Sweden, 1.10.2013 - 31.12.2014
• Director of the Aalto NeuroImaging ANI
Chairman of the session:
• The multiple facets of coherence analysis: From neurophysiology to clinical applications, Biomag 2014, Halifax, Canada, 24. - 28.8.
Pre-examiner of a thesis:
• Selja Vaalto, Functional muscle representations in cerebral cortex and usedependent plasticity in motor cortices, Itä-Suomen yliopisto, Kuopio, Finland,
10.1.
Referee:
• Cerebral Cortex
Khaymovich Ivan
Referee:
• JETP Letters
• Journal of Experimental and Theoretical Physics
• Journal of Low Temperature Physics
Koskinen Miika
Referee:
• Neurocomputing
Interview:
• Elokuva opettaa aivotutkijoita, Helsingin Sanomat (HS Tiede), Newspaper, Suomi,
16.5.
Krusius Matti
Membership in distinguished societies:
•
•
•
•
Finnish Academy of Sciences and Letters
Academia Europea
Fellow member, American Physical Society
Institute of Physics, UK
Member of scientific associations:
• Finnish Physical Society
• Individual ordinary member, European Physical Society
Editor of scientific journal:
• Journal of Low Temperature Physics
Annual Report 2014
– 121 –
Kujala Jan
Referee:
• Frontriers in Psychology
• Human Brain Mapping
• Neuropsychobiology
Menorét Mathilde
Referee:
• Neuroimage
Nora Anni
Member of the organizing committee:
• Annual Meeting of the Doctoral program Brain&Mind, Kirkkonummi, Finland, 11.
- 12.9.
Referee:
• PLOS ONE
Paraoanu Sorin
Chairman of the session:
• Morning session - mesoscopic physics and quantum information, Advanced manybody and statistical methods in mesoscopic physics II, Brasov, Romania, 1. - 5.9.
• Workshop on Entanglement, Decoherence, and Quantum Control (EDQC2014),
Buffalo (NY), U.S.A., 14. - 14.11.
Interview:
• Jurnal (News), RTT (Radio Televiziunea Transilvania), TV, Brasov, Romania, 4.9.
Pekola Jukka
Membership in distinguished societies:
• Finnish Academy of Sciences and Letters
• Finnish Academy of Technical Sciences
Member of scientific associations:
• Finnish Physical Society
Position of trust in scientific organizations:
• Member of the Research Council for Natural Sciences and Engineering, Academy
of Finland, Finland, 1.1.2013 - 31.12.2015
• Member of IUPAP C5, Commission on Low Temperature Physics
• Advisory board member, Karlsruhe Institute of Technology, DFG, Center for
Functional nanostructures, CFN, Karlsruhe, Germany
• Scientific Advisory Board review, National Enterprise for nanoScience and nanotechnology NEST, Pisa, Italy, 10. - 12.11.
• Expert member, Otaniemi Research Infrastruture for Micro and Nanotechnologies
(OtaNano) steering group, Espoo, Finland
Annual Report 2014
– 122 –
Leader position in a scientific organization:
• Chairman, Micronova Advisory Board Espoo, Finland
Member of the organising committee:
• Electronic Quantum Transport in Condensed Matter, the 27th International Conference on Low Temperature Physics, LT27, Buenos Aires, Argentina, 6. - 13.8.
Member of the editorial board:
• Physical Review B
Editor of scientific journal:
• Journal of Low Temperature Physics
Referee:
•
•
•
•
•
Journal of Low Temperature Physics
Nature Materials
Nature Nanotechnology
Physical Review B
Physical Review Letters
Opponent:
• Dania Kambly, Counting statistics in interacting nano-scale conductors, University of Geneva, Geneva, Switzerland, 12.2.
• Lucas Casparis, Ultra-Low Electron Temperatures in Nanostructured Samples,
University of Basel, Basel, Switzerland, 24.10.
• Andreas Heimes, Karlsruhe Institute of Technology, Karlsruhe, Germany, 11.12.
Renvall Ville
Referee:
• Human Brain Mapping
Saira Olli-Pentti
Member of scientific associations:
• Academy Club for Young Scientists of the Finnish Academy of Science and Letters
Salmelin Riitta
Membership in distinguished societies:
• Fellow of the International Society for Functional Source Imaging
• Finnish Academy of Sciences and Letters
• Academia Europaea
Position of trust in scientific organizations:
• Member of External Advisory Panel, Washington University, NIH/Human Connectome Project Consortium Washington University & University of Minnesota,
St. Louis, MN, USA, 1.10.2010 - 31.12.2015.
• Member, President's Science and Technology Advisory Council, European Union,
EU Commission, Brussels, Belgium, 1.1.2013 - 31.12.2014
Annual Report 2014
– 123 –
• Member of Steering Committee, EuropaNova, The Conference EUROPA, France,
1.8.2013 - 31.12.2014
• Member of the Physiology & Medicine Section Committee, Academia Europaea,
London, United Kingdom, 1.1.2014 - 31.12.2016.
Pre-examiner of a thesis:
• Joao Correia, Neural Coding of Speech and Language: fMRI and EEG studies,
Maastricht University, Maastricht, The Netherlands, 24.9.
Member of the editorial board:
• Brain Topography
• Language, Cognition and Neuroscience
• PeerJ
Editor of scientific journal:
• Frontiers in Brain Imaging Methods
• Human Brain Mapping
Savin Alexander
Referee:
• Journal of Low Temperature Physics
Seol Jaeho
Leader position in a scientific organization:
· Vice Present, The society of Korean Scientists and Engineers in Finland (KOSES),
1.1. - 31.12.
Membership of the organising committee:
• EU-Korea Conference on Science and Technology 2014, Vienna, Austria, 22. 25.7.
Secretary of the conference or organising committee:
• 2014 KOSES Autumn Symposium and Annual Meeting, Helsinki, Finland, 29.11.
Chairman of the session:
• Biomedical data processing and visualization, EU-Korea Conference on Science
and Technology 2014, Vienna, Austria, 22. - 25.7.
Sillanpää Mika
Interview:
• Quantum-mechanical behaviour at the macro-scale, EU Projects Magazine, Magazine, Bristol, United Kingdom, 2.5.
Silvanto Juha
Interview:
• Miksi baaritappelussa neroksi muuttunut amerikkalainen tuli Suomeen? Suomalainen huippututkija vastaa, Helsingin Sanomat, Newspaper, Finland, 10.5.
Annual Report 2014
– 124 –
• Suomalaistutkijoilla rooli oudon nerouden tutkimisessa, Helsingin Sanomat,
Newspaper, Suomi, 11.5.
Vanni Simo
Interview:
• Miksi baaritappelussa neroksi muuttunut amerikkalainen tuli Suomeen? Suomalainen huippututkija vastaa, Helsingin Sanomat, Newspaper, Finland, 10.5.
Virtanen Pauli
Member of scientific associations:
• Academy Club for Young Scientists of the Finnish Academy of Science and Letters.
Referee:
•
•
•
•
Journal of Low Temperature Physics
New Journal of Physics
Physical Review B
Physical Review Letters
Volovik Grigory
Membership in distinguished societies:
• Deutsche Academie der Naturforscher Leopoldina (the German Academy of Sciences Leopoldina)
• Finnish Academy of Sciences and Letters
Position of trust in scientific organizations:
• evaluator of proposals for ERC, Brussels, Belgium
Chairman of the session:
• International Winter School for Theoretical Physics, Kourovka-35, Ekaterinburg,
Russia, 23.2. - 1.3.
• Landau Days – 2014, Chernogolovka, Russia, 22. - 25.6.
Editor:
• JETP Letters
• Physical Review Letters, Divisional Associate Editor
Member of the editorial board:
• JETP Letters
• Physical Review Letters
Opponent:
• Yulia Shchadilova, Theoretical investigation of the mechanisms of the operation of
single molecules absorbed on the surface of solids, Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow, Russia, 10.11.
Interview:
• Small world, big physics, New Scientist, Magazine, Espoo, Finland, 10.3.
Annual Report 2014
– 125 –
PUBLICATIONS
KVANTTI
1.
2.
Chalapat K., Timonen J., Huuppola M., Koponen L., Johans C., Ras R.H.A.,
Ikkala O., Oksanen M.A., Seppälä E., and Paraoanu G.S., Ferromagnetic resonance in epsilon-Co magnetic composites, Nanotechnology 25, p. 485707
(2014).
Paraoanu, G.S., Recent Progress in Quantum Simulation Using Superconducting
Circuits, J. Low Temp. Phys. 175, p. 633-654 (2014).
NANO and NEMS
3.
4.
5.
6.
7.
8.
9.
Jalkanen, P., Tuboltsev, V., Marchand, B., Savin, A., Puttaswamy, M., Vehkamäki, M., Mizohata, K., Kemell, M., Hatanpää, T., Rogozin, V., Räisänen, J.,
Ritala, M., and Leskelä, M., Magnetic Properties of Polycrystalline Bismuth
Ferrite Thin Films Grown by Atomic Layer Deposition, J. Phys. Chem. Lett. 5, p.
4319-4323 (2014). (NANO)
Laitinen, A., Oksanen, M., Fay, A., Cox, D., Tomi, M., Virtanen, P., and Hakonen, P.J., Electron−Phonon Coupling in Suspended Graphene: Supercollisions by Ripples, Nano Lett. 14, p. 3009-3013 (2014). (NANO)
Lähteenmäki, P., Vesterinen, V., Hassel, J., Paraoanu, G.S., Seppä, H., and Hakonen, P., Advanced Concepts in Josephson Junction Reflection Amplifiers, J.
Low Temp. Phys. 175, 868-876 (2014). (NANO)
Oksanen, M., Uppstu, A., Laitinen, A., Cox, D.J., Craciun, M.F., Russo, S., Harju, A., and Hakonen, P., Single-mode and multimode Fabry-Perot interference in
suspended graphene, Phys. Rev. B 89, p. 121414(R) (2014). (NANO)
Sillanpää, M.A. and Hakonen, P.J., Optomechanics: Hardware for a quantum
network, Nature (News&Views), 507, p. 45–46 (2014). (NEMS)
Song, X. and Oksanen, M. and Li, J. and Hakonen, P.J. and Sillanpää, M.A.,
Graphene optomechanics realized at microwave frequencies, Phys. Rev. Lett.
113, p. 027404 (2014). (NANO)
Tuboltsev, V., Savin, A., Rogozin, V. D., and Räisänen, J., Silicon-based Coulomb blockade thermometer with Schottky barriers, Appl. Phys. Lett. 104,
163507 (2014). (NANO)
PICO
10. Ankerhold, J.A., and Pekola, J.P., Heat due to system-reservoir correlations in
thermal equilibrium, Phys. Rev. B 90, p. 075421 (2014).
11. Aref, T., Averin, A., van Dijken, S., Ferring, A., Koberidze, M., Maisi, V.F.,
Nquyend, H.Q., Nieminen, R.M., Pekola, J.P., and Yao, L.D., Characterization
of aluminum oxide tunnel barriers by combining transport measurements and
transmission electron microscopy imaging, J. Appl. Phys. 116, p. 073702 (2014).
12. Courtois, H. Hekking, FW.J., Nguyen, H.Q., Winkelmann, C.B., Electronic
Coolers Based on Superconducting Tunnel Junctions: Fundamentals and Applications, J. Low Temp. Phys. 175, p. 799-812 (2014).
13. Faivre, T., Golubev, D., and Pekola, J.P., Josephson junction based thermometer
and its application in bolometry, J. Appl. Phys. 116, 094302 (2014).
Annual Report 2014
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14. Golubev, D., Lombardi, F., and Bauch, T., Effect of heating on critical current of
YBCO nanowires, Physica C: Superconductivity and its Applications 506, pp.
174-177 (2014).
15. Gramich, V., Gasparinetti, S., Solinas, P., and Ankerhold, J., Lamb-Shift Enhancement and Detection in Strongly Driven Superconducting Circuits, Phys.
Rev. Lett. 113, p. 027001 (2014).
16. Heimes, A., Maisi, V.F., Golubev, D.S., Marthaler, M., Schön, G., and Pekola, J.
P., Tunneling and Relaxation of Single Quasiparticles in a NormalSuperconductor-Normal Single Electron Transistor, Phys. Rev. B 89, 014508
(2014).
17. Jabdaraghi, R.N., Meschke, M., and Pekola, J., Non-hysteretic superconducting
quantum interference proximity transistor with enhanced responsivity, Appl.
Phys. Lett. 104, 082601 (2014).
18. Khaymovich, I.M., Mel'nikov, A.S., and Buzdin, A.I., Phase transitions in the
domain structure of ferromagnetic superconductors, Phys. Rev. B 89, 094524
(2014).
19. Koski, J.V., Maisi, V.F., Sagawa, T., and Pekola, J.P., Experimental observation
of the role of mutual information in the nonequilibrium dynamics of a maxwell
demon, Phys. Rev. Lett. 113, p. 030601 (2014).
20. Maisi, V.F., Kambly, D., Flindt, C. and Pekola, J.P., Full counting statistics of
Andreev tunneling, Phys. Rev. Lett. 112, 036801 (2014).
21. Meschke, M., Nanosized electronic cooler combined with superconducting proximity effect thermometry, J. Low Temp. Phys. 175, p. 838-849 (2014).
22. Pekola, J.P., Koski, J.V., and Averin, D.V., Refrigerator based on the Coulomb
barrier for single-electron tunneling, Phys. Rev. B 89, 081309(R) (2014).
23. Scheller, C.P., Heizmann, S., Bedner, K., Giss, D., Meschke, M., Zumbuhl,
D.M., Zimmerman, J.D., and Gossard, A.C., Silver-epoxy microwave filters and
thermalizers for millikelvin experiments, Appl. Phys. Lett. 104, p. 211106
(2014).
24. Taupin, M., Howald, L., Aoki, D., and Brison, J.-P.†, Superconducting gap of
UCoGe probed by thermal transport, Phys. Rev. B90, 180501(R) (2014).
ROTA
26. Eltsov, V.B., Hänninen, R., and Krusius, M., Quantum turbulence in superfluids
with wall-clamped normal component, Proc. Nat. Acad. Sci. (PNAS), 111, p.
4711-4718 (2014).
27. Heikkinen, P.J., Autti, S., Eltsov, V.B., Haley, R.P., Zavjalov, V.V., Microkelvin
thermometry with Bose-Einstein condensates of magnons and applications to
studies of the AB interface in superfluid 3He, J. Low Temp. Phys. 175, p. 681705 (2014).
28. Heikkinen, P.J., Autti, S., Eltsov, V.B., Hosio, J.J., Krusius, M., and Zavjalov,
V.V., Relaxation of Bose-Einstein Condensates of Magnons in Magneto-Textural
Traps in Superfluid 3He-B, J. Low Temp. Phys. 175, p. 3-16 (2014).
29. Hietala, N. and Hänninen, R., Comment on "Motion of a helical vortex filament
in superfluid 4He under the extrinsic form of the local induction approximation",
Phys. Fluids 26, p. 019101 (2014).
30. Hänninen, R., and Baggaley, A.W., Vortex filament method as a tool for computational visualization of quantum turbulence, Proc. Nat. Acad. Sci. (PNAS), 111,
p. 4667-4674 (2014).
Annual Report 2014
– 127 –
31. Krusius, M., and Pekola, J., Ultralow temperatures and nanophysics, J. Low
Temp. Phys. 175, p. 631-632 (2014).
THEORY
32. Ballestar, A., Heikkilä, T., & Esquinazi, P. Size dependence of the Josephson
critical behavior in pyrolytic graphite TEM lamellae, Supercond. Sci. Technol.
27, p. 115014 (2014).
33. Esquinazi, P., Heikkilä, T.T., Lysogorskiy, Y.V., Tayurskii, D.A., and Volovik,
G.E., On the superconductivity of graphite interfaces, JETP Letters/Pis'ma v
Zhurnal Éksperimetal'noi i Teoreticheskoi Fiziki 100, p. 374-378 (2014).
34. Heikkilä, T.T., Massel, F., Tuorila, J., Khan, R., and Sillanpää, M.A., Enhancing
Optomechanical Coupling via the Josephson Effect, Phys. Rev.Lett. 112, p.
203603 (2014).
35. Katsnelson, M.I. and Volovik, G.E., Topological matter: graphene and superfluid 3He, J. Low Temp. Phys. 175, p. 655-666 (2014).
36. Kopnin, N.B. and Heikkilä, T.T., Surface superconductivity in rhombohedral
graphite (Ch. 9), in Book: Carbon-based new superconductors - towards high
temperature superconductivity, pp. 231-264 (2014).
37. Kopnin, N.B., Mel'nikov, A.S., Sadovskyy, I.A., and Vinokur, V.M., Weak links
in proximity-superconducting two-dimensional electron systems, Phys. Rev. B
89, p. 081402 (2014).
38. Makhlin, Yu., Silaev, M., and Volovik, G.E., Topology of the planar phase of
superfluid He3 and bulk-boundary correspondence for three-dimensional topological superconductors, Phys. Rev. B 89, p. 174502 (2014).
39. Ojanen, T., and Borkje, K., Ground-state cooling of mechanical motion in the
unresolved sideband regime by use of optomechanically induced transparency,
Phys. Rev. A 90, p. 013824 (2014).
40. Ozaeta, A., Virtanen, P., Bergeret, F.S., and Heikkilä, T.T., Predicted Very Large
Thermoelectric Effect in Ferromagnet-Superconductor Junctions in the Presence
of a Spin-Splitting Magnetic Field, Phys. Rev. Lett. 112, p. 057001 (2014).
41. Pöyhönen, K., Westström, A., Röntynen, J., and Ojanen, T., Majorana states in
helical Shiba chains and ladders, Phys. Rev. B 89, p. 115109 (2014).
42. *Silaev, M., Heikkilä, T.T., Virtanen P., Lindblad equation approach for the full
counting statistics of work and heat in driven quantum systems, Phys. Rev. E 90,
p. 022103 (2014).
43. Silaev, M.A. and Volovik, G.E., Andreev-Majorana bound states in superfluids,
Zhurnal Éksperimental'noi i Teoreticheskoi Fiziki 146, p. 1192-1209 (2014).
44. Virtanen, P., Energy transport via multiphonon processes in graphene, Phys.
Rev. B 89, p. 245409 (2014).
45. Virtanen, P., and Giazotto, F., Thermal transport through ac-driven transparent
Josephson weak links, Phys. Rev. B 90, p. 014511/1-12 (2014).
46. Volovik, G. E. and Zubkov, M. A., Emergent Horava gravity in graphene, Ann.
Phys. 340, p. 352-368 (2014).
47. Volovik, G. E., and Zubkov, M. A., Emergent Weyl fermions and the origin of i
= in quantum mechanics, JETP Lett. 99, p. 481-486 (2014).
48. Volovik, G. E. and Zubkov, M. A., Emergent Weyl spinors in multi-fermion systems, Nucl. Phys. B 881, p. 514-538 (2014).
49. Volovik, G. E. and Zubkov, M. A., Higgs Bosons in Particle Physics and in
Condensed Matter, J. Low Temp. Phys. 175, p. 486-497 (2014).
Annual Report 2014
– 128 –
50. Volovik, G.E. and Zubkov, M.A., Mirror as polaron with internal degrees of
freedom, Phys. Rev. D 90, p. 087702 (2014).
µKI
51. Ahlstrom, S.L., Bradley, D.I., Clovecko, M., Fisher, S.N., Guénault, A.M.,
Guise, E.A., Haley, R.P., Kolosov, O., Kumar, M., McClintock, P.V.E., Pickett,
G.R., Polturak, E., Poole, M., Todoshchenko, I., Tsepelin, V., Woods, A.J., Response of a Mechanical Oscillator in Solid 4He, J. Low Temp. Phys. 175, p. 140146 (2013).
52. Ahlstrom, S.L., Bradley, D.I., Človečko, M., Fisher, S.N., Guénault, A.M.,
Guise, E.A., Haley, R.P., Kumar, M., McClintock, P.V.E., Pickett, G.R., Polturak, E., Poole, M., Todoshchenko, I., Tsepelin, V., and Woods, A.J., Plastic
Properties of Solid 4He Probed by a Moving Wire: Viscoelastic and Stochastic
Behavior Under High Stress, J. Low Temp. Phys. 175 p. 147-153 (2014).
53. Manninen, M.S., Kaikkonen, J.-P., Peri, V., Rysti, J., Todoshchenko, I. and Tuoriniemi, J., Excitation and Detection of Surface Waves on Normal and Superfluid
3
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54. Manninen, M.S., Rysti, J., Todoshchenko, I., and Tuoriniemi, J., Quasiparticle
damping of surface waves in superfluid 3He and 4He, Phys. Rev. B 90, p. 224502
(2014).
55. Rysti, J., Manninen, M.S., and Tuoriniemi, J., Measurements on melting pressure, metastable solid phases, and molar volume of univariant saturated Helium
mixture, J. Low Temp. Phys. 175 p. 739-754 (2014).
56. Rysti, J. and Tuoriniemi, J., Quartz Tuning Forks and Acoustic Phenomena: Application to Superfluid Helium, J. Low. Temp. Phys. 177, p. 133-150.
57. Todoshchenko, I., Kaikkonen, J.-P., Blaauwgeers, R., Hakonen, P.J., and Savin,
A., Dry demagnetization cryostat for sub-millikelvin helium experiments: Refrigeration and thermometry, Rev. Sci. Instr. 85, p. 085106 (2014).
58. Tuoriniemi, J.T., Manninen, M.S., and Rysti, J., Pressure dependent attenuation
peaks for quartz tuning forks in superfluid 4He at mK temperatures, J. Phys.
Conf. Ser. 568, p. 012023 (2014).
OTHER LOW TEMPERATURE AND NANOPHYSICS
59. Govenius, J., Lake, R. E., Tan, K. Y., Pietilä, V., Julin, J. K., Maasilta, I. J., Virtanen, P., and Möttönen, M., Microwave nanobolometer based on proximity Josephson junctions, Physical Review B, 90, p. 064505 (2014).
60. Ollikainen, T., Ruokokoski, E., and Möttönen, M., Creation and dynamics of
two-dimensional skyrmions in antiferromagnetic spin-1 Bose-Einstein condensates, Physical Review A, 89, p. 033629 (2014).
61. Ray, M.W., Ruokokoski, E., Kandel, S., Möttönen, M., and Hall, D.S., Observation of Dirac monopoles in a synthetic magnetic field, Nature, 505, p. 657660 (2014).
62. Rossi, A., Tanttu, T., Tan, K.Y., Iisakka, I., Zhao, R.C., Chan, K.W., Tettamanzi, G.C., Rogge, S., Dzurak, A.S., and Möttönen, M., An Accurate SingleElectron Pump Based on a Highly Tunable Silicon Quantum Dot, Nano Letters,
14, p. 3405-3411 (2014).
63. Salmilehto J., Solinas, P., and Möttönen, M., Quantum driving and work, Physical Review E, 89, p. 052128 (2014).
Annual Report 2014
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ATTENTION AND MEMORY
64.
65.
66.
67.
68.
69.
70.
Anurova, I., Renier, L.A., De Volder, A.G., Carlson, S., and Rauschecker, J.P.,
Relationship between cortical thickness and functional activation in the early
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Boldt, R., Gogulski, J., Guzman-Lopez, J., Carlson, S., Pertovaara, A., Twopoint tactile discrimination ability is influenced by temporal features of stimulation, Experimental Brain Research, 232, p. 2179-2185 (2014).
Boldt, R., Seppä, M., Malinen, S., Tikka, P., Hari, R., and Carlson, S., Spatial
variability of functional brain networks in early-blind and sighted subjects,
NeuroImage, 95, p. 208-216 (2014).
Carlson, S., Miten muisti on selitettävissä?, Duodecim 130, p. 2431-2434
(2014).
Hayashi, M.J., Kantele, M., Walsh, V., Carlson, S., and Kanai, R., Dissociable
neuroanatomical correlates of subsecond and suprasecond time perception,
Journal of Cognitive Neuroscience, 26, p. 1685-1693 (2014).
Jiang, P., Tokariev, M., Aronen, E.T., Salonen, O., Ma, Y., Vuontela, V., and
Carlson, S., Responsiveness and functional connectivity of the scene-sensitive
retrosplenial complex in 7-11-year-old children, Brain and Cognition 92C, p.
61-72 (2014).
Okamoto, Y., Kitada, R., Tanabe, H.C., Hayashi, M.J., Kochiyama, T.,
Munesue, T., Ishitobi, M., Saito, D.N., Yanaka, H.T., Omori, M., Wada, Y.,
Okazawa, H., Sasaki, A.T., Morita, T., Itakura, S., Kosaka, H., and Sadato, N.,
Attenuation of the contingency detection effect in the extrastriate body area in
autism spectrum disorder, Neuroscience Research, 87, p. 66-76 (2014).
CliniMEG
71.
72.
Forss, N., and Vartiainen, N., Krooniseen kipuun liittyvien aivomuutosten
kuvantaminen, Duodecim 130, p. 1507-1514 (2014).
Kirveskari, E., Vartiainen, N.V., Kallio-Laine, K., Kalso, E., and Forss, N.,
Normal laser-evoked cortical responses in patients with chronic hemibody pain,
European Journal of Pain, p. (2014).
HUMAN SYSTEMS NEUROSCIENCE and CLINIMEG
73.
74.
75.
76.
Clumeck, C., Sarah Suarez Garcia, S., Bourguignon, M., Wens, V., Op de
Beeck, M., Marty, B., Deconinck, N., Soncarrieu, M-V., Goldman, S.,
Jousmäki, V., Van Bogaert, P., and De Tiège, X., Preserved coupling between
the reader’s voice and the listener’s cortical activity in autism spectrum disorders, PLoS One, 9, p. e92329 (2014).
Hari, R., Bourguignon, M., Piitulainen, H., Smeds, E., De Tiège, X., and
Jousmäki, V., Human primary motor cortex is both activated and stabilizes during observation of other person’s phasic motor actions, Philosophical Transactions B369, p. 20130171 (2014).
Kauppi, J.P., Pajula, J., and Tohka, J., A versatile software package for intersubject correlation based analyses of fMRI, Frontiers in Neuroinformatics, 8, p.
2 (2014).
Kivistö, K., Nevalainen, P., Lauronen, L., Tupola, S., Pihko, E., and KivitieKallio, S., Somatosensory and auditory processing in opioid-exposed newborns
with neonatal abstinence syndrome: a magnetoencephalographic approach,
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77.
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81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
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Koskinen, M. and Seppä, M., Uncovering cortical MEG responses to listened
audiobook stories, NeuroImage, 100, p. 263-270 (2014).
Lahnakoski, J.M., Glerean, E., Jääskeläinen, I.P., Hyönä, J., Hari, R., Sams, M.,
and Nummenmaa, L., Synchronous brain activity across individuals underlies
shared psychological perspectives, NeuroImage, 100C, p. 316-324 (2014).
Lamminmäki, S., Parkkonen, L., and Hari, R., Neuromagnetic responses to amplitude-modulated binaural tones, speech, and music, Ear and Hearing 35, p.
461-467 (2014).
Lankinen, K., Saari, J., Hari, R., and Koskinen, M., Intersubject consistency of
cortical MEG signals during movie viewing, NeuroImage, 92, p. 217–224
(2014).
Lindsberg, P.J., Castrén, E., Korkeila, J., Alho, H., Erkinjuntti, T., Isometsä, E.,
Kalso, E., Karlsson, H., Marttunen, M., Pihko, H., Tienari, P., Wartiovaara, A.,
Jäkälä, P., Kälviäinen, R., Soininen, H., Tiihonen, J., Karlsson, H., Rinne, J.,
Roine, R.O., Elovaara, I., Tamminen, T., Öhman, J., Majamaa, K., and Hari, R.,
Aivosairaudet ovat kalleimmat kansantautimme, Duodecim, 130, p. 1721–1730
(2014).
Malinen, S., Renvall, V., Hari, R., Functional parcellation of the human primary somatosensory cortex to natural touch, European Journal of Neuroscience,
39, p. 738-743 (2014).
Mandel, A., Helokunnas, S., Pihko, E., Hari, R., Neuromagnetic brain responses to other person’s eye blinks seen on video, European Journal of Neuroscience, 40, p. 2576-2580 (2014).
Nevalainen, P., Lauronen, L., and Pihko, E., Development of human somatosensory cortical functions – what have we learned from magnetoencephalography:
A review, Frontiers in Human Neuroscience, 5, p. 158 (2014).
Nevalainen, P., Rahkonen, P., Pihko, E., Lano, A., Vanhatalo, S., Andersson, S.,
Autti, T., Valanne, L., Metsäranta, M., and Lauronen, L., Evaluation of somatosensory cortical processing in extremely preterm infants at term with MEG
and EEG, Clinical Neurophysiology, online June 2014.
Nummenmaa L., and Hari, R., Aivot rakastavat seuraa, Tiede (April), p. 32-36
(2014).
Nummenmaa, L., Glerean, E., Hari, R., and Hietanen, J.K., Bodily maps of emotions, Proceedings of the National Academy of Sciences of the United States of
America (PNAS), 111, p. 646-651 (2014).
Nummenmaa, L., Saarimäki, H., Glerean, E., Gotsopoulos, A., Jääskeläinen,
I.P., Hari, R., and Sams, M., Emotional speech synchronizes brains across listeners and engages large-scale dynamic brain networks., NeuroImage, 102, p.
498-509 (2014).
Nummenmaa, L., Smirnov, D., Lahnakoski, J.M., Glerean, E., Jääskeläinen,
I.P., Sams, M., and Hari, R., Mental action simulation synchronizes action – observation circuits across individuals., Journal of Neuroscience, 34, p. 748-757
(2014).
Pihko, E., Nevalainen, P., Vaalto, S., Laaksonen, K., Mäenpää, H., Valanne, L.,
and Lauronen, L., Reactivity of sensorimotor oscillations is altered in children
with hemiplegic cerebral palsy, Human Brain Mapping, 35, p. 4105-4117
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Raij T.T., Korkeila J., Joutsenniemi K., Saarni S.I., Riekki T.J.J., Association of
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92.
93.
94.
95.
96.
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Ramkumar, P., Parkkonen, L., and Hyvärinen, A., Group-level spatial independent component analysis of Fourier envelopes of resting-state MEG data,
NeuroImage, 86, p. 480–491 (2014).
Renvall, V., Nangini, C., Hari, R., All that glitters is not BOLD: Inconsistencies
in functional MRI, Scientific Reports, 4, p. 3920 (2014).
Riekki, T., Lindeman, M., Raij, T.T., Supernatural believers attribute more intentions to random movement than skeptics: An fMRI study, Social Neuroscience, 9, p. 400-411 (2014).
Wens, V., Bourguignon, M., Goldman, S., Marty, B., Op de Beeck, M., Clumeck, C., Mary, A., Peigneux, P., Van Bogaert, P., Brookes, M.J., De Tiege, X.,
Inter- and intra-subject variability of neuromagnetic resting state networks,
Brain Topography, 27, p. 620-634 (2014).
Wens, V., Mary, A., Bourguignon, M., Goldman, S., Marty, B., de Beeck, M.
O., Van Bogaert, P., Peigneux, P., De Tiege, X., About the electrophysiological
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(2014).
IMAGING LANGUAGE
97.
Helenius, P., Sivonen, P., Parviainen, T., Isoaho, P., Hannus, S., Kauppila, T.,
Salmelin, R., and Isotalo, L., Abnormal functioning of the left temporal lobe in
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98. Hultén, A., Karvonen, L., Laine, M., and Salmelin, R., Producing speech with a
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99. Kim, C.H., Lee, S., Kim, J.S., Seol, J., Yi, SW., Chung, C.K., Melody effects on
ERANm elicited by harmonic irregularity in musical syntax, Brain Research,
1560, p. 36-45 (2014).
100. Kujala, J., Sudre, G., Vartiainen, J., Liljeström, M., Mitchell, T., and Salmelin,
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101. Ylinen, S., Nora, A., Leminen, A., Hakala, T., Huotilainen, M., Shtyrov, Y.,
Mäkelä, J.P., and Service, E., Two distinct auditory-motor circuits for monitoring speech production as revealed by rehearsal-elicited suppression of auditory
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MULTIMODAL NEUROIMAGING, SIGNAL ANALYSIS, AND MODELING
102. Gramfort, A., Luessi, M., Larson, E., Engemann, D., Strohmeier, D., Brodbeck,
C., Parkkonen, L., and Hämäläinen, M., MNE software for processing MEG and
EEG data, NeuroImage 86, p. 446-460 (2014).
VISION SYSTEMS NEUROSCIENCE
103. Bona, S., Herbert, A., Toneatto, C., Silvanto, J., and Cattaneo, Z., The causal
role of the lateral occipital complex in visual mirror symmetry detection and
grouping: An fMRI-guided TMS study, Cortex, 51, p. 46-55 (2014).
104. Bona, S. and Silvanto, J., Accuracy and confidence of visual short-term memory
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105.
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Cattaneo, Z., Bona, S., Bauer, C., Silvanto, J., Herbert, A.M., Vecchi, T., and
Merabet, L.B., Symmetry detection in visual impairment: Behavioral evidence
and neural correlates, Symmetry, 6, p. 427-443 (2014).
Cattaneo, Z., Bona, S., Monegato, M., Pece, A., Vecchi, T., Herbert, A.M., Merabet, L.B., Visual symmetry perception in early onset monocular blindness,
Visual Cognition, 22, p. 963-974 (2014).
Cattaneo, Z., Renzi, C., Bona, S., Merabet, L.B., Carbon, C.C., Vecchi, T.,
Hemispheric asymmetry in discriminating faces differing for featural or configural (second-order relations) aspects, Psychonomic Bulletin and Review, 21, p.
363-369 (2014).
Cattaneo, Z., Renzi, C., Casali, S., Silvanto, J., Vecchi, T., Papagno, C., and
D'Angelo, E., Cerebellar vermis plays a causal role in visual motion discrimination, Cortex, 58, p. 272-280 (2014).
Renzi, C., Vecchi, T., D' Angelo, E., Silvanto, J., and Cattaneo, Z., Phosphene
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Salminen-Vaparanta, N., Vanni, S., Noreika, V., Valiulis, V., Móró, L., and
Revonsuo, A., Subjective characteristics of TMS-induced phosphenes originating in human V1 and V2, Cerebral Cortex, 24, p. 2751-2760 (2014).
Silvanto, J., Is primary visual cortex necessary for visual awareness?, Trends in
Neurosciences, 37, p. 618-619 (2014).
Silvanto, J., Why is "blindsight" blind? A new perspective on primary visual
cortex, recurrent activity and visual awareness, Consciousness and Cognition,
p. (2014).
Soto, D., and Silvanto, J., Reappraising the relationship between working
memory and conscious awareness, Trends in Cognitive Sciences, 18, p. 520-525
(2014).
Annual Report 2014