Download Electron Dynamics on Surfaces and Nanostructures November 05

Electron Dynamics on Surfaces and
Nanostructures
November 05, 2014 - November 07, 2014
ZCAM Zaragoza
Sergio Diaz-Tendero
Universidad Autonoma de Madrid, Spain
Cristina Díaz
Universidad Autónoma de Madrid, Spain
Fernando Martin
Autonomous University of Madrid, Spain
Francisco Garcia-Vidal
Universidad Autonoma de Madrid, Spain
Johannes Feist
Universidad Autónoma de Madrid, Spain
1 Description
In everyday life we regularly come across phenomena related to materials and surface
science. Indeed advances on this area have spurred the development of more efficient
technologies and many more are expected in the near future. For example, among the
new materials developed in recent years, photovoltaic devices deserve particular
consideration. Specifically, organic solar cells have been proposed as an efficient
alternative [1,2] to the standard silicon-based cells. The development of these devices
relies on the latest advances in materials science, which ultimately require in-depth
knowledge of the interaction of atoms and molecules deposited on surfaces when they
are exposed to the interaction with light: photoinduced charge transfer processes.
An important tool holding significant promise for future applications are surface
plasmon polaritons (SPPs), collective light-matter excitations bound to metal surfaces
at subwavelength scales. Through their strong concentration of optical fields and
precise controllability, SPPs can enable novel approaches for controlling electronic
processes on surfaces. For example, it has been shown that they can be used to tune
the work function of a metal [8], induce molecular dissociation through electron heating
[9], and allow chemical identification of single molecules [10]. Furthermore, SPPs can
support ultrafast (few-femtosecond) dynamics due to their potentially large energy
bandwidth. This could enable control of surface processes on both nanometer spatial
scales and femtosecond temporal scales.
Fundamental electronic processes such as electron capture, electron transfer and
electron excitation mechanisms, taking place on surfaces and nanostructures, have an
intrinsic importance in different fields of chemistry and physics. For instance, in the
near future, miniaturization of electronic devices will bring us to the atomic limit, with
single molecules being the key building blocks. In this context, a new multidisciplinary
field of research known as molecular electronics has emerged in the last decade (see
e.g. [3,4]). The analysis of electron transport through junctions between molecules or
between one molecule and one surface is also a crucial point [5,6]. The transient
formation of excited electronic states in surfaces constitutes another example (see e.g.
[7]). These states play a role in a diversity of phenomena in molecular electronics as
well as in chemical reactions at surfaces.
One fundamental challenge to be faced by surface and materials scientists, working in
theoretical modelling of atoms and molecules interacting with surfaces and
nanostructures, is the development of new theoretical methods for computing the
dynamics of electronically excited states, collective electron excitations including
plasmons, and electron transport.
Key references
[1] C. Brabec et al., in ‘ Organic Photovoltaics: Concepts and Realization’ , Springer, Berlin, (2003).
[2] A. Goetzberger et al., Mater. Sci. Res., 40, 1 (2003).
[3] P.F. Barbara et al., J. Phys. Chem. 100, 13148 (1996).
[4] A. Nitzan, Ann. Rev. Phys. Chem. 52, 681 (2001).
[5] P. Jelinek et al., Phys. Rev. Lett. 101, 176101 (2008).
[6] H. Park et al., Nature 407, 57 (2000)
[7] Thematic Issue: Photochemistry and Photophysics on Surfaces, Chem Rev. 106, Issue 10 (2006).
[8] J.A. Hutchison et al., Advanced Materials 25, 2481 (2013).
[9] S. Mukherjee et al., Nano Letters 13, 240 (2013).
[10] R. Zhang et al., Nature 498, 82 (2013).
2 Program
Day 1 - Wednesday November 5, 2014
• 13:30 to 15:00 - Lunch
• 15:00 to 15:15 - Welcome
• 15:15 to 16:00 - Presentation - Jean-Pierre Gauyacq
Correlation effects in magnetic excitation induced by tunneling electrons in
adsorbed atomic chains
• 16:00 to 16:45 - Presentation - Roberto Robles
Site- and orbital-dependent charge and spin manipulation in supported transition
metal phthalocyanines
• 16:45 to 17:15 - Coffee Break
• 17:15 to 18:00 - Presentation - Amadeo López Vázquez de Parga
Adding functionalities to epitaxial graphene by self assembly on or below its
surface
• 18:00 to 18:30 - Presentation - Pedro B. Coto
Simulation of
electron transfer processes
molecule-semiconductor interfaces
at
molecule-metal
and
• 18:30 to 18:45 - Presentation - Maitreyi Robledo Relaño
Dehydrogenation of benzene under an electric current
• 18:45 to 19:00 - Presentation - Daniele Stradi
Electronic transport in gated graphene nanoconstrictions.
Day 2 - Thursday November 6, 2014
• 9:00 to 9:45 - Presentation - Nicolás Lorente
Magnetic dynamics of adsorbed atomic objects.
• 9:45 to 10:30 - Presentation - Andrés Arnau
Electronic and magnetic properties os metal organic coordination networks
• 10:30 to 11:00 - Coffee Break
• 11:00 to 11:45 - Presentation - Peter Saalfrank
Electrons, light, and nuclear degrees of freedom: from spectroscopy to
photochemistry at metal surfaces
• 11:45 to 12:00 - Presentation - Aitzol Iturbe
Intrinsic magnetic oscillations associated with phonon modes in materials with
strong spin-orbit interaction
• 12:00 to 12:45 - Presentation - Giovanni Manfredi
Electron and spin dynamics in thin metal films
• 12:45 to 13:15 - Presentation - Asier Eiguren
Helmholtz fermi surface harmonics: an efficient approach for treating anisotropic
problems involving fermi surface integrals
• 13:15 to 15:30 - Lunch
• 15:30 to 16:15 - Presentation - Matthias Kling
Attosecond photoemission from nanostructures
• 16:15 to 16:30 - Presentation - Javier Cuerda
Spatio-temporal dynamics of lasing action in plasmonic systems
• 16:30 to 17:15 - Presentation - Mark I. Stockman
Spaser in quantum regime
• 17:15 to 17:45 - Presentation - Jean Christophe TREMBLAY
Laser-driven electron dynamics of a germanium/silicon core-shell system
• 21:00 to 0:00 - Dinner
Day 3 - Friday November 7, 2014
• 9:30 to 10:15 - Presentation - Ralf Vogelgesang
Ultrafast coherent charge and energy transfer: from plasmonic-excitonic hybrid
systems to artificial light harvesting systems
• 10:15 to 11:00 - Presentation - James A. Hutchison
Chemical dynamics in confined optical cavities
• 11:00 to 11:30 - Coffee Break
• 11:30 to 12:15 - Presentation - Luis Martín Moreno
One-dimensional transport of few photons strongly coupled to quantum systems.
• 12:15 to 12:45 - Presentation - Kirsten Andersen
Plasmons on the atomic scale: quantum theory of plasmon eigenmodes in
nanostructures
• 12:45 to 13:30 - Presentation - Rubén Esteban
Influence of electron tunneling in ultranarrow plasmonic gaps
• 13:30 to 15:30 - Lunch
• 15:30 to 16:15 - Presentation - Tue Gunst
Inelastic scattering and current-induced forces in nano-conductors
• 16:15 to 16:30 - Presentation - Peio G. Goiricelaya
Electronic band structure and phonon dispersion relation at the tl/si(111) surface
from first principles calculations.
• 16:30 to 17:15 - Presentation - Ulrich Höfer
Resonance trapping at interfaces
3 Abstracts
Correlation effects in magnetic excitation induced by tunneling electrons
in adsorbed atomic chains
Jean-Pierre Gauyacq[1], Nicolás Lorente
Institut des Sciences Moléculaires d'Orsay, ISMA. URM 8214, Bât 351, Univeristé
Paris-Sud, 91405 Orsay CEDEX, France
ICN2-CSIC, ICN2 Building, Campus UAB, 08193 Bellaterra, Barcelona, Spain
Electron tunnelling from an STM (Scanning Tunnelling Microscope) tip through a magnetic
adsorbate can change the direction of the magnetic moment of the adsorbate, i.e.modify the
magnetic state of the adsorbate. The development of high-resolution, ultra low-T and
high-magnetic field STM allowed these processes to be analyzed experimentally in details (see
e.g. [1]), A magnetic excitation can be seem as a spin angular momentum transfer between
electron and adsorbate and as such, it bears strong resemblances with rotational excitation
processes that are associated with orbital angular momentum transfer [2]. We have developed a
theoretical treatment of these excitation processes based on the sudden approximation for the
magnetic interactions [3]. A wide range of problems can be tackled with it: splin-flip of individual
magnetic adsorbates at surface, excitation of nano-objects, spin waves, relaxation of magnetic
excitations, reversal of supported quantal magnets.In the case of chains of magnetic atoms
adsocrbed on surfaces, correlation between the various spins in the chain can strongly affect
the excitation processes. Indeep, injecting an electron into one of the atoms in the chain can flip
the spin of this atoms, but flipping the entire chain has to involve mixing between the various
atoms in the chain. In the talk, two aspects will be presented: how the entanglement of the
various atoms spins in an antiferro-magnetic chain allows the magnetic excitation [4,5] and how
decoherence induced by the substrate deeply affects the magnetic dynamics of the chain.
[1] C. F. Hirjibehedin, C.-Y. Lin, A. F. Otte, M. Tenes, C. P. Luntz, B. A. Jones and A. J. Heinrich, Science
317, 1199 (2007)
[2] J. Schaffert, M. C. Cottin, A. Sonntag, H. Karacuban, C. A. Bobisch, N. Lorente, J. P. Gauyacq and R.
Möller, Nature Mat. 12, 223 (2013)
[3] J. P. Gauyacq, N. Lorente and F. D. Novaes, Prog. Surf. Sci. 87 (2008)
[4] S. Loth, S. Baumann, C. P. Luntz, D. M. Eigler and A. J. Heinrich, Science 335, 196 (2012)
[5] J. P. Gauyacq, S. M. Yaro, X. Cartoixà and N. Lorente, Phys. Rev. Lett. 110, 087201 (2013)
Site- and orbital-dependent charge and spin manipulation in supported
transition metal phthalocyanines
Roberto Robles[1]
ICN2-CSIC
Site- and orbital-dependent charge and spin manipulationin supported transition metal
phthalocyanines
Adding Functionalities to Epitaxial Graphene by Self Assembly on or
below its Surface
Amadeo López Vázquez de Parga[1]
Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia),
and Dep. Física de la Materia Condensada, Universidad Autónoma de Madrid,
Cantoblanco 28049, Madrid, Spain.
Among the set of extraordinary electronic, mechanical or optical properties of graphene intrinsic
ordered magnetic behaviour or strong spin-orbit interaction are not included. By growing
epitaxially graphene on single crystal metal surfaces under Ultra High Vacuum (UHV) conditions
[1] and adsorbing molecules on it or intercalating heavy atoms below it, we show how to add
magnetic functionalities to graphene. We discuss two examples: i)
Achieving long range
magnetic order on a monolayer of TCNQ adsorbed on graphene /Ru(0001). In this case, the
graphene monolayer is spontaneously nanostructured forming an hexagonal array of 100 pm
high nanodomes with a periodicity of 3 nm [2] and localized electronic states [3]. Cryogenic
Scanning Tunnelling Microscopy (STM) and Spectroscopy and Density Functional Theory
simulations show that isolated TCNQ molecules deposited on gr/Ru(0001) acquire charge from
the substrate and develop a sizeable magnetic moment, which is revealed by a prominent
Kondo resonance [4]. The magnetic moment is preserved upon dimer and monolayer formation.
The self-assembled molecular monolayer develops spatially extended spin-split electronic
bands with only the majority band filled, thus becoming a 2D organic magnet whose predicted
spin alignment in the ground state is visualized by spin-polarized STM at 4.6 K [5].The long
range magnetic order is originated by the charge transfer from graphene to TCNQ (which
creates the magnetic moments) plus the self-assembly of the molecular adlayer on the
periodically corrugated graphene layer (which creates spin-polarized intermolecular bands
where the added electrons delocalize). Examples will be shown where the adsorbed molecules
accept charge and develop magnetic moments, but do nor form bands and, accordingly, no
long-range order appear (F4-TCNQ on graphene/Ru(0001)), or where molecules do form similar
bands, but they are not populated because there is no charge transfer to the molecules (TCNQ
on gr/Ir(111)). No long range magnetic order develops in theses cases. ii) Introducing a giant
spin-orbit interaction on graphene/Ir(111) by intercalation of Pb. The intercalation of an ordered
array of Pb atoms below graphene results in the appearance a series of equally spaced, sharp
peaks in the differential conductance, as revealed by laterally resolved Tunnelling Spectroscopy
at 4.6 K. The vicinity of Pb enhances the, usually negligible, spin-orbit interaction of graphene.
The spatial variation of the spin-orbit coupling when going from graphene intercalated with Pb to
graphene directly deposited on Ir(111) creates a pseudo-magnetic field that originates
pseudo-Landau levels [6].
[1] A.L. Vázquez de Parga et al, Phys. Rev. Lett. 100, 056807 (2008)
[2] B. Borca et al, Phys. Rev. Lett. 105, 036804 (2010)
[3] D. Stradi et al, Phys. Rev. Lett. 106, 186102 (2011)
[4] M. Garnica et al. Nano Letters 14, 4560 (2014)
[4] M. Garnica et al, Nature Physics 9, 368 (2013)
[5] F. Calleja et al, submitted
Simulation of Electron Transfer Processes at Molecule-Metal and
Molecule-Semiconductor Interfaces
Pedro B. Coto[1], Veronika Prucker [1], Óscar Rubio-Pons [1], Michel Bockstedte [1],
Haobin Wang [2], Michael Thoss [1]
Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
[1] Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
[2] New Mexico State University, Las Cruces, New Mexico, USA
Heterogeneous electron transfer (ET) in molecular systems at semiconductor or metal surfaces
is a key step in many processes relevant to Chemistry, Physics and Material Science. Important
applications where this process plays a fundamental role include photonic energy conversion in
nanocrystalline dye-sensitized solar cells, in which photoexcitation triggers the injection of an
electron from an excited electronic state of a dye molecule into the conduction band of a
semiconductor, and charge transport in nanoscale molecular junctions. Recently, we have
developed an approach to study the dynamics of ET in molecule-metal and
molecule-semiconductor systems that combines a first-principles characterization of the
systems with an accurate quantum treatment of the dynamics.1,2 In this contribution, we
present the results obtained in the simulation of ET processes in perylene-titanium dioxide
dye-semiconductor systems2 and self-assembled monolayers of nitrilesubstituted alkanethiolate
molecules adsorbed at metal surfaces.3,4 In particular, we investigate the roles that the
symmetry of the donor state and the molecular structure of the spacer groups have in the
dynamics of the charge transfer process.
1. Kondov, I.; Cizek, M.; Benesch, C.; Wang, H.; Thoss, M. J. Phys. Chem. C 2007, 111, 11970.
2. Li, J.; Wang, H.; Persson, P.; Thoss, M. J. Chem. Phys. 2012, 137, 22A529.
3. Blobner, F.; Coto, P. B.; Allegretti, F.; Bockstedte, M.; Rubio-Pons, O.; Wang, H.; Allara, D. L.;
Zharnikov, M.; Thoss, M.; Feulner P. J. Phys. Chem. Lett. 2012, 3, 436.
4. Prucker, V.; Rubio-Pons, O.; Bockstedte, M.;Wang, H.; Coto, P. B.; Thoss, M. J. Phys. Chem. C 2013,
117, 25334.
Dehydrogenation of Benzene under an electric current
Maitreyi Robledo Relaño[1], Paula Abufager [1], Sergio Díaz-Tendero [2], Manuel
Alcamí [2], Fernando Martín [2,3], Nicolas Lorente [1]
Universidad Autónoma de Madrid, Spain
[1] Institut Catala de Nanociencia i Nanotecnologia (ICN2), Barcelona, Spain
[2] Universidad Autónoma de Madrid, Spain
[3] Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia),
Madrid, Spain
In the latest years there has been an increasing interest on forcing chemical reactions by using
a Scanning Tunnelling Microscope (STM) [1, 2]. The tunnelling electrons created by the
microscope can induce vibrational or electronic excitations, achieving different phenomena of
the adsorbates placed at the surface. Thus, the STM is a way to control chemical reactions on
the nano scale. Of course, STM not only can induce chemical reactions, but it also provides us
with real-space images of molecules adsorbed on surfaces, giving us the chance of determining
adsorption sites and space orientation of the molecules. We present here the study of a single
benzene molecule, placed in between two Cu(100) leads. Through this copper leads, a finite
potential will be created, affecting thus, the structure of the C6H6 molecule, i.e. forcing its
dehydrogenation. We show how this phenomenon can be analyzed through the change in the
atomic forces experienced by each pair of C-H atoms. Moreover, the electronic structure of the
organic molecule will be modified as the current in between the two Cu leads is increased. Our
transport calculations will involve a simple Siesta calculation of the electrodes and a TranSiesta
one of the scattering region. TranSiesta [3] is a method to solve the electronic structure of a
finite open system, which has been placed in between two semi-infinite metallic sheets. A finite
potential is then applied between the two sheets, giving rise to an electric current. TranSiesta
solves the electronic density from the DFT Hamiltonian using techniques based on the Green’ s
function, instead of the commonly used diagonalization method. Therefore, before performing a
TranSiesta calculation, one must perform a Siesta one, where those Green’ s Function are
calculated, as well as the charge density of the open system [4].
[1] P. Avouris, Acc.Chem. Res. 18, 95 (1995)
[2] W. Ho,Acc. Chem. Res. 31,567 (1998)
[3]http://departments.icmab.es/leem/siesta/Documentation/Manuals/siesta-3.1-manual/node89.html
[4] M.Brandbyge et al., Phys. Rev. B 65, 165401 (2002)
Electronic transport in gated graphene nanoconstrictions.
Daniele Stradi[1], Nick P. Andersen, Tue Gunst, Mads Brandbyge
DTU Nanotech
DTU Nanotech.
Graphene nanoconstrictions are fundamental building blocks in graphene-based
nanoelectronic, in which an electronic current is passed through a short graphene ribbon at the
narrowest point [1]. In this contribution, using a state-of-the-art approach based on Density
Functional Theory and the Non-Equilibrium Green’ s Function method [2], we investigate the
impact of electrostatic gating at finite bias voltages in models graphene nanoconstrictions,
showing how gating and chemical functionalization can be effectively employed to control the
transmission characteristics and the potential drop across the device.
[1] Tue Gunst, Jing-Tao Lü, Per Hedegård, Mads Brandbyge Phonon excitation and instabilities in biased
graphene nanoconstrictions Physical Review B 88, 161401 (2013)
[2] Mads Brandbyge, José-Luis Mozos, Pablo Ordejón, Jeremy Taylor, Kurt Stokbro Density-functional
method for nonequilibrium electron transport Physical Review B 65, 165401 (2002)
Magnetic dynamics of adsorbed atomic objects.
Nicolás Lorente[1], Roberto Robles1, Richard Korytár1,2, Jean-Pierre Gauyacq3,
ICN2-CSIC, ICN2 Building, Campus UAB, 08193 Bellaterra (Barcelona) Spain
1.ICN2-CSIC, ICN2 Building, Campus UAB, 08193 Bellaterra (Barcelona) Spain
2.Institut für Nanotechnologie, Karlsruher Institut für Technologie,
Hermann-von-Helmholtzplatz 1, D-76344 Eggenstein-Leopoldshafen, Germany
3.Institut des Sciences Moléculaires d’ Orsay, ISMO, Unité mixte CNRS-Université
Paris-Sud, UMR 8214, Bâtiment 351, Université Paris-Sud, F-91405 Orsay CEDEX,
France
The scanning tunneling microscope (STM) is instrumental when analyzing matter on the atomic
scale. Not only has it sub-atomic spatial resolution, but it is well below the milli-eV energy scale,
which allows it to map the spectral function of complex systems with unprecedented resolution.
The advent of milli-Kelvin techniques is also of fundamental importance when studying
magnetism on the nanoscale. An emerging full field of magnetic inelastic electron spectroscopy
(IETS) [1] is permitting us to unravel the microscopic origin of magnetism on the nanoscale. Our
work deals with the understanding and numerical simulation of all these phenomena. I will
present numerical studies on metallic phthalocyanine molecules on Ag (100) [2] which gives
unprecedented insight in molecular magnetism on a non-magnetic host. Correlations, high spins
and the Kondo effect can be found here. Excitations are naturally seen by the STM-based
experiments, and excitations are very interesting when combined with the Kondo effect [3].
[1] C.F. Hirjibehedin, C.-Y. Lin, A.F. Otte, M. Ternes, C.P. Lutz, B.A. Jones, and A.J. Heinrich, Science
317, 1199 (2007).
[2] A. Mugarza, N. Lorente, P. Ordejón, C. Krull, S. Stepanow, M.-L. Bocquet, J. Fraxedas, G. Ceballos,
and P. Gambardella, Phys. Rev. Lett. 105, 115702 (2010); A. Mugarza, R. Robles, C. Krull, R. Korytár, N.
Lorente, and P. Gambardella, Phys. Rev. B 85, 155437 (2012).
[3] Richard Korytár, Nicolás Lorente and Jean-Pierre Gauyacq, Phys. Rev. B 85, 125434 (2012).
Electronic and Magnetic Properties os Metal Organic Coordination
Networks
Andrés Arnau[1]
Departamento de Fisica de Materiales UPV/EHU, Centro de Fisica de Materiales
(CFM) and Donostia International Physics Center (DIPC), Donostia-San Sebastian,
Spain
In this talk, I will present a few examples of metal-organic coordination networks formed by
metal atoms and strong electron acceptor molecules on Au(111). First, I will focus on the
electronic properties of two different systems, Au-F4TCNQ and Mn-TCNQ. In the case of
Au-F4TCNQ, surface Au adatom seggregation is induced upon F4TCNQ adsorption, while in
Mn-TCNQ the Mn atoms are co-evaporated with the TCNQ molecules. Next, I will consider the
magnetic properties of Ni-TCNQ and Mn-TCNQ coordination networks in which spin magnetic
moments localized at the metal atoms can be ferro- or antiferromagnetically coupled, depending
on subtle details of the electronic structure close to the Fermi level. In particular, we find that the
presence of a spin polarized hybrid band with electrons delocalized along the whole system
constituents is determinant for the appearance of ferromagnetic coupling between metal atoms,
as it is the case of Ni-TCNQ but not of Mn-TCNQ. Possible applications of interest, like the
growth of thin ferromagnetic overlayers on topological insulators will be discussed as well.
Electrons, Light, and Nuclear Degrees of Freedom: From Spectroscopy to
Photochemistry at Metal Surfaces
Peter Saalfrank[1], T. Klamroth [1], I Andrianov [1], Ch. Huber [1], G. Materzanini [1], J.
I. Juaristi [2,3,4], M. Alducin [3,4], M. Blanco-Rey [2,3], R. Díez-Muiño[3,4], G. Füchsel
[1], S. Monturet [1], J. C. Tremblay [1]
Intitut für Chemie, Universität Potsdam, D-14476 Potsdam-Golm, Germany
[1] Intitut für Chemie, Universität Potsdam, D-14476 Potsdam-Golm, Germany
[2]Departamento de Física de Materiales, Facultad de Químicas UPV/EHU, Apartado
1072, 20018 Donostia-San Sebastián, Spain
[3] Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4,
20018 Donostia-San Sebastián, Spain
[4]Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Paseo Manuel de
Lardizabal 5, 20018 Donostia-San Sebastián, Spain
Electrons near metal surfaces can efficiently couple to light or nuclear degrees of freedom, or
both. In the talk, we shall first study the coupling of metal electrons to light, by recalling some
older theoretical work of laser-driven and laser-probed, electron dynamics near metals: The
two-photon-photo-emission (2PPE) spectroscopy of image potential states at metal surfaces [1],
and of 'solvated electrons' at water-ice covered Cu(111) [2]. The 2PPE spectra are simulated
either by solving effective one-electron time-dependent Schrödinger equations, or an N-electron
Schrödinger equation using configuration interaction methodology.The coupling of electrons to
nuclear motion is a second topic, At thin metal films, so-called quantum size effects (QSE) may
emerge. For the example of Pb films of increasing thinckness, it was shown by periodic density
functional theory that the 'electron spillout' above the Pb layer is an oscillating function of film
thickness, due to QSE [3]. This observation, first made experimentally by helium atom scattering
(HAS), is then used to study theoretically a possible impact of QSE on vibrational lifetimes of
vibrating H atoms adsorbed on Pb overlayers, due to coupling of nuclear motion to electron hole
pair (EHP) excitations within the metal [4]. This is done with the help of a recently proposed, ab
initio molecular dynamics with electronic friction (AIMDEF) approach.Finally, if time permits, we
shall briefly touch light-driven, coupled electon-nuclear dynamics. An example is EHP-mediated
photodesorption of small molecules (such as H2), from surfaces (such as Ru(0001)), which we
treat either by frictional molecular dynamics, or by open-system density matrix theory [5]
[1] T. Klamroth, P. Saalframk and U, Höfer. Phys. Rev. B 64, 035420 (2001): P. Saalframk, T. Klamroth,
Ch. Huber and P. Krause. Isr. J. Chem 45, 205 (2005)
[2] I. Andrianov, T. Klamroht, P. Saalfrank, U. Bovensiepen, C. Gahl, M. Wölf. J. Chem. Phys. 122. 234710
(2005)
[3] G. Materzanini, P. Saalframk, P. J. D. Lindan. Phys. Rev. B 63, 235405 (2001)
[4] P. Saalfrank, J. I. Juaristi, M. Alducin, M. Blanco-Rey, R. Díez-Muiño, submitted (2014)
[5] G. Füchsel, T. Klamroth, S. Monturet, P. Saalfrank, Phys. Chem. Chem. Phys. 13, 8659 (2011)
Intrinsic Magnetic Oscillations Associated with Phonon Modes in
Materials with Strong Spin-Orbit Interaction
Aitzol Iturbe[1], Idoia G.Gurtubay [1 ][2], Asier Eiguren [1][2]
University of the Basque Country, UPV/EHU, Spain
[1] Unibersity of the Basque Country, UPV/EHU, Spain
[2] Donostia International Physics Center (DIPC), Donostia, Spain
We have demonstrated that in systems with large spin-orbit interaction the propagating
vibrational modes are inherently accompanied with a magnetic oscillation. We have shown that
this phenomena is very general and applies even in nominally non-magnetic materials.
Moreover, we have seen that the contribution of this phenomena to the electron-phonon matrix
elements may be of the order of 10% of the total, in a highly non-trivial way, as the matrix
elements come as the overlap of three spinorial objects.We have considered a single WSe2
mono-layer as a test example, where the real space and phonon crystal momentum
dependence of the phonon associated magnetic modulation has been analyzed in detail.
Electron and spin dynamics in thin metal films
Giovanni Manfredi[1], Paul-Antoine Hervieux
Institut de Physique et Chimie des Matériaux, CNRS and Université de Strasbourg,
BP 43, F-67034 Strasbourg, France
Institut de Physique et Chimie des Matériaux, CNRS and Université de Strasbourg, BP
43, F-67034 Strasbourg, France
The ultrafast electron dynamics in optically excited metallic nanostructures is of great
importance for both fundamental studies and technological applications to materials science.
Thin metal films of submicron thickness are typical examples of nanostructures and are widely
used in modern high-speed electronic and opto-electronic devices. In such systems, the
switching time can nowadays approach the femtosecond time domain. On this time scale, the
electron distribution is out of thermal equilibrium. In order to control the energy consumption, it
is therefore important to develop a better understanding of the electron transport and the energy
relaxation in this temporal regime.In this presentation I will review the efforts undertaken by our
group to study this topic over the last few years. First, we have performed self-consistent
simulations of the electron dynamics and transport in thin metal films, using a semiclassical
Vlasov-Poisson model [1, 2, 3]. The dynamical properties are strongly influenced by the finite
size of the system and the presence of surfaces. Our results showed that: (i) heat transport is
ballistic and occurs at a velocity close to the Fermi speed; (ii) after the excitation energy has
been absorbed by the film, slow nonlinear oscillations appear, with a period proportional to the
film thickness: these oscillations are due to nonequilibrium electrons bouncing back and forth on
the film surfaces; (iii) except for trivial scaling factors, the above transport properties are
insensitive to the excitation energy and the initial electron temperature. Secondly, we have
analyzed the impact of quantum effects on the dynamics. The quantum evolution was simulated
using the Wigner equation [4] and a quantum hydrodynamic (fluid) model [5]. We observed a
classical-quantum transition at low enough excitation energies: above a certain threshold the
evolution is classical and the above Vlasov results are recovered, particularly the ballistic
oscillations; below the threshold quantum effects play a role and the nonlinear oscillation period
differs from the ballistic value. The effect of dissipation and decoherence was also investigated
[6].Finally, I will present new advances related to recent experiments [7] on the coherent
coupling between a femtosecond laser pulse and the magnetization of a ferromagnetic thin film.
For strong pulses, relativistic effects come into play, also contributing to the spin dynamics
(spin-orbit coupling). This scenario requires the modelling of the nonlinear dynamics of a
quantum-relativistic system of many electrons interacting with an electromagnetic field. Some
results based on the Dirac and Pauli equations will be shown [8, 9].
[1] G. Manfredi and P. -A. Hervieux, Phys. Rev. B 70, 201402 (R) (2004).
[2] G. Manfredi and P. -A. Hervieux, Phys. Rev. B 72, 155421 (2005).
[3] G. Manfredi and P. -A. Hervieux, Optics Letters 30, 3090 (2005).
[4] R. Jasiak, G. Manfredi and P. -A. Hervieux, New J. Phys. 11, 063042 (2009).
[5] N. Crouseilles, P. -A. Hervieux, and G. Manfredi, Phys. Rev. B 78, 155412 (2008).
[6] R. Jasiak, G. Manfredi, and P.-A. Hervieux, Phys. Rev. B 81, 241401(R) (2010).
[7] J.-Y. Bigot et al, Nat. Phys. 5, 515 (2009).
[8] A. Dixit et al, Phys. Rev. A 88, 032117 (2013); Y. Hinschberger, P.-A. Hervieux, Phys. Lett. A 376, 813
(2012).
[9] J. Hurst, O. Morandi, G. Manfredi, and P.-A. Hervieux, Eur. Phys. J. D 68, 176 (2014).
Helmholtz Fermi surface harmonics: an efficient approach for treating
anisotropic problems involving Fermi surface integrals
Asier Eiguren[1], Idoia G Gurtubay
Materia Kondentsatuaren Fisika Saila, Zientzia eta Teknologia Fakultatea, Euskal
Herriko
Unibertsitatea UPV/EHU, 644 Postakutxatila, E-48080 Bilbo, Basque Country, Spain
Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal, E-20018,
Donostia,
Basque Country, Spain
Materia Kondentsatuaren Fisika Saila, Zientzia eta Teknologia Fakultatea, Euskal
Herriko
Unibertsitatea UPV/EHU, 644 Postakutxatila, E-48080 Bilbo, Basque Country, Spain
Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal, E-20018,
Donostia,
Basque Country, Spain
We present a new efficient numerical approach for representing anisotropic physical quantities
and/or matrix elements defined on the Fermi surface (FS) of metallic materials. The method
introduces a set of numerically calculated generalized orthonormal functions, which are the
solutions of the Helmholtz equation defined on the FS, where the periodicity of the reciprocal
space is treated as a boundary condition. The main motivation of the approach is to handle
anisotropic many-body problems very efficiently. In this context we demonstrate how our theory
reduces, by several orders of magnitude, the computational effort when applied to several well
know many-body theoretical models such as the electron-phonon or the Anderson impurity
problem. Moreover, the method is demonstrated to be very robust in handling problems with any
crystal structure or topology of the FS. We illustrate the method showing applications on several
relevant surface and bulk systems.
Asier Eiguren and Idoia G. Gurtubay. New J. Phys. 16, 063014 (2014)
Attosecond Photoemission from Nanostructures
Matthias Kling[1]
Physik Department, Ludwig-Maximilians-Universität, D-85748 Garching
One of the most fundamental processes in nature is the photoemission of electrons from solid
targets. This process forms the basis for optoelectronics, where light can trigger electron
transfer, amplification, and emission, and electron injection and excitation can result in the
emission of light. The decrease in the dimensions of electronic and optoelectronic circuitry is
directly linked to a potential increase in their speed of operation. On nanometer (10-9 m)
dimensions electrons typically move on attosecond to femtosecond timescales (10-18 – 10-15
s). The inherent link of these spatial and temporal dimensions has recently led to the
development of the new field of attosecond nanophysics.The talk will introduce new
measurement concepts that permit to obtain information with highest time and spatial resolution.
It will be shown, how these have been recently applied to obtain microscopic information about
the photoemission of electrons from nanoparticles and nanoantennas using extreme ultraviolet
light. The talk will also introduce how strong fields can both lead to photoemission when the
workfunction is higher than the photon energy, and how electron emission in such strong fields
can be controlled with the electric field waveform of visible light. Finally, the optical properties of
nanomaterials, in contrast to their bulk solid counterparts, can heavily depend on their shape
and size, which permits tempering with ultrafast optoelectronic properties using these
parameters. As an example, we will show how the dimensions of nanoparticles strongly
influence their near-fields leading to effects such as nanofocusing, which can be exploited to
accelerate freed electrons and create bursts of attosecond electron pulses with extremely high
energies.
Spatio-temporal dynamics of lasing action in plasmonic systems
Javier Cuerda[1], Felix Rüting, Jorge Bravo-Abad, Francisco J. García-Vidal
Universidad Autónoma de Madrid, Spain
Lasing action at nanoscale dimensions has attracted a great deal of attention recently, due to its
fundamental and applied interest. Plasmonic nanostructures offer the possibility to overcome
the diffraction limit, thus becoming ideal systems to achieve subwavelength lasing action [1].
Successful demonstrations have been reported for metallic structures such as nanoparticles [2,
3], holes [4], and waveguides [5], by their integration with gain materials. The fast development
of plasmonic lasers makes it necessary to develop a complete and efficient theoretical
framework that can provide insight into recent experimental results and guide new
developments. In this contribution, we present a novel computational formalism based on a
time-domain generalization of the finite-element method, which can account for the full
spatio-temporal dynamics of the non-linear interaction of the gain medium and the
highly-nonuniform electric field of plasmonic resonances. We apply this formalism to
theoretically analyze several recent experiments on loss compensation and lasing action in
plasmonic structures. Our results show that the developed framework enables us to unveil the
microscopic physical origin of how lasing action is achieved in different plasmonic systems [6,
7]. In addition, our theoretical framework allows us to optimize the lasing characteristics of the
considered structures, with respect to both the geometrical parameters and the emission
properties of the molecules forming the gain medium.
[1] J. Bravo-Abad, F. J. García-Vidal, “ Plasmonic lasers: A sense of direction” , Nature Nanotechnology
(News and views) 8, 479 (2013).
[2] M. A. Noginov, G. Zhu, A. M. Belgrave, R. Bakker, V.M. Shalaev, E. E. Narimanov, S. Stout, E. Herz, T.
Suteewong, and U. Wiesner “ Demonstration of a spaser-based nanolaser” , Nature 460, 1110– 1112 ,
(2009).
[3] W. Zhou, M. Dridi, J. Y. Suh., C. H. Kim, D. T. Co, M. R. Wasielewski, G. C. Schatz, T. W. Odom,
“ Lasing action in strongly coupled plasmonic nanocavity arrays” , Nature Nanotechnology 8, 506– 511
(2013).
[4] F. van Beijnum, P. J. van Veldhoven, E. J. Geluk, M. J. A. de Dood, G. W. ’ t Hooft, and M. P. van
Exter “ Surface Plasmon Lasing Observed in Metal Hole Arrays” , Physical Review Letters 110, 206802
(2013).
[5] S. Kéna-Cohen, P. N. Stavrinou, D. D. C. Bradley, S. A. Maier, “ Confined Surface Plasmon-Polariton
Amplifiers” , Nano Lett. 2013, 13, 1323-1329 (2013).
[6] F. Rüting, J. Cuerda, J. Bravo-Abad, F. J. García-Vidal, “ Lasing action assisted by long-range surface
plasmons” , Laser Photonics Rev. 8, 5 (2014).
[7] J. Cuerda, F. Rüting, F. J. García-Vidal, J. Bravo-Abad, “ Theory of lasing action in plasmonic crystals”
(submitted).
Spaser in Quantum Regime
Mark I. Stockman[1]
Center for Nano-Optics and Department of Physics and Astronomy, Georgia State
University, Atlanta, GA 30302, USA
Nanoplasmonics deals with collective electron dynamics on the surface of metal nanostructures,
which arises due to excitations called surface plasmons. Nanoplasmonics has numerous
applications in science, technology, biomedicine, environmental monitoring, and defense. Until
recently, all the effects, elements, and devices in nanoplasmonics have been passive: they use
external optical energy, always losing a fraction of it to heat and leakage radiation. An active
device generating energy directly on the nanoscale has been spaser (surface plasmon
amplification by stimulated emission of radiation). We briefly consider quantum theory and latest
results on spaser as an ultrafast quantum generator and amplifier of nanoplasmonic fields [1-4],
ultrabright nanolabel, and highly-efficient nanosensor [2]. We present latest original results:
electrical nanospaser in the extreme quantum regime [5] and graphene nanospaser [6].
[1] Y.-J. Lu, C.-Y. Wang, J. Kim, H.-Y. Chen, M.-Y. Lu, Y.-C. Chen, W.-H. Chang, L.-J. Chen, M. I.
Stockman, C.-K. Shih, and S. Gwo, All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning
Mechanism for Single-Mode Lasing, Nano Lett. 14, 4381– 4388 (2014).
[2] R.-M. Ma, S. Ota, Y. Li, S. Yang, and X. Zhang, Explosives Detection in a Lasing Plasmon Nanocavity,
Nat. Nano 9, 600-604 (2014).
[3] T. P. H. Sidiropoulos, R. Roder, S. Geburt, O. Hess, S. A. Maier, C. Ronning, and R. F. Oulton,
Ultrafast Plasmonic Nanowire Lasers near the Surface Plasmon Frequency, Nat. Phys. advance online
publication, doi: 10.1038/nphys3103 (2014).
[4] M. Stockman, Plasmonic Lasers: On the Fast Track, Nat. Phys. advance online publication, doi:
10.1038/nphys3127 (2014).
[5] D. Li and M. I. Stockman, Electric Spaser in the Extreme Quantum Limit, Phys. Rev. Lett. 110,
106803-1-5 (2013).
[6] V. Apalkov and M. I. Stockman, Proposed Graphene Nanospaser, Light Sci. Appl. 3, e191-1-6 (2014).
Laser-Driven Electron Dynamics of a Germanium/Silicon Core-Shell
System
Jean Christophe TREMBLAY[1], Gunter Hermann
Freie Universität Berlin, Berlin, Germany
Freie Universität Berlin, Berlin, Germany
Nanometer-scale semiconductor crystallites have attracted increasing interest over the last
decade, both from theory and experiment. Their natural tendency to confine electrons in all
three spatial dimensions qualifies them as promising components for future electronic devices,
such as in quantum computers. One of the most sought-after characteristics of these quantum
dots is the possibility to tailor specific optical and electronic properties by varying their size and
composition. Understanding the physics involved in such devices by investigating the electronic
structure and laser-driven electron dynamics can be very instructive. Whereas large quantum
dots are often studied using scalable approximate methods, such as tight-binding or the k-p
perturbation theory, these approaches provide little insight in the microscopic mechanisms at
work. On the other hand, smaller structures can be investigated using systematically
improvable, wave function-based ab-initio methods, which can serve as benchmark for the more
approximate methods while also giving a more precise picture of the transient electron
dynamics. In the present contribution, we study the laser-driven electron dynamics in
nanometer-size semiconductor core-shell systems as model quantum dots, with a particular
emphasis on increasing electron trapping efficiency. Small germanium impurities embedded in a
silicon host matrix forms the quantum dot, which are chosen so as to retain the structural
characteristics of self-assembled germanium islands on a silicon (001) surface, covered by a
silicon wetting layer. As a prelude to the electron dynamics, we study the system static excited
electronic states and their associated properties using the configuration interaction (CI) method
at the singles level. The evaluation of the one-electron densities of the CIS eigenstates supplies
evidence for interlevel transitions where electron density is getting trapped in the germanium
region. In order to perform a laser-driven electron dynamics along the identified path, we use
the reduced density matrix variant of the time-dependent configuration interaction method. This
allows us to further include the coupling of the local core-shell structure with the silicon
environment in the electron dynamics. Employing a simple physically motivated model for the
electron-phonon coupling, it is shown that electron trapping by localized optical excitations in
our model Ge/Si quantum dot is robust with respect to phonon-induced pure dephasing.
Ultrafast coherent charge and energy transfer: from plasmonic-excitonic
hybrid systems to artificial light harvesting systems
Ralf Vogelgesang[1]
Oldenburg University
In the first part, we will concentrate on a system of stronglycoupled excitons and surface
plasmon polaritons, made ofJ-aggregates and metallic nanostructured film. Probing the
opticalresponse of the system by angle-resolved spectral interferometry,we find evidence for
two different channels of energy transfer:Coherent dipole-dipole interaction on the one hand
and anincoherent exchange due to the spontaneous emissions of a photon byone emitter and
its subsequent reabsorption by another. Theinterplay between both pathways results in a
pronouncedmodification of the radiative damping. Within a coupled oscillatormodel this behavior
can be attributed to the formation of super-and subradiant polariton states, which is confirmed
by probing theultrafast nonlinear response of the polariton system. In the second part of the
presentation we investigate the primarycharge-transfer process in prototype systems for
organicphotovoltaic devices, such as supramolecular triads or blends ofconjugated polymers
and fullerene derivatives. By a combinedapproach using high time-resolution femtosecond
spectroscopy andtime-dependent density functional theory, we find compellingevidence that the
driving mechanism of the photoinduced currentgeneration cycle is a correlated wavelike motion
of electrons andnuclei on a timescale of few tens of femtoseconds.
Chemical Dynamics in Confined Optical Cavities
James A. Hutchison[1], Thibault Chervy, Shaojun Wang, Jino George, Cyriaque Genet,
Thomas W. Ebbesen
ISIS & icFRC, Université de Strasbourg & CNRS, Strasbourg, France.
ISIS & icFRC, Université de Strasbourg & CNRS, Strasbourg, France.
This presentation will outline recent experimental work in our laboratory focusing on the
chemical and electronic properties of organic materials when placed inside nanoscale optical
cavities. When the optical density of the material oscillators reaches a threshold value, coherent
exchange of photons with the cavity can occur, leading to the formation of organic
exciton-polaritons. The potential of these hybrid light-matter states has yet to be fully explored,
particularly within the domain of chemistry [1]. We discuss a range of recent experimental
studies on both metal Fabry-Perot cavities and plasmonic substrates, including optical
pump-probe measurements of exciton-polariton dynamics, and electronic measurements on the
organic materials in these cavities. We attempt to square the results of these studies with
current theory.
[1] J.A. Hutchison, T. Schwartz, C. Genet, E. Devaux and T.W. Ebbesen, Angew. Chem. Int. Ed. 51 1592
(2012)
One-Dimensional Transport of Few Photons Strongly Coupled to Quantum
Systems.
Luis Martín Moreno[1], E. Sanchez-Burillo [1], J. J. Garcia-Ripoll [2], D. Zueco[2]
Instituto de Ciencia de Materiales de Aragon and Departamento de Fisica de la
Materia Condensada, CSIC-Universidad de Zaragoza, E-50009, Zaragoza, Spain
[1] Instituto de Ciencia de Materiales de Aragon and Departamento de Fisica de la
Materia Condensada, CSIC-Universidad de Zaragoza, E-50009, Zaragoza, Spain
[2] 2Instituto de Física Fundamental, IFF-CSIC, Serrano 113-B, 28006 Madrid, Spain
Light-matter interaction is one of the most fascinating topics in physics. Its enhancement using
few-level-systems (FLS) in cavities has lead to the rich field of Cavity Quantum
Electrodynamics. More recently, it has been realized that enhanced light-matter interaction can
be realized in quasi-one-dimensional waveguides, such as dielectric waveguides,
superconducting strips, photonic crystal waveguides, plasmonic waveguides, etc. Different
types of waveguides may work at different frequency ranges and different physical conditions
(like temperature), but they all profit from the confinement of the field and the reduced
dimensionality in light propagation. Several results are known in these one-dimensional
quantum-electrodynamics (1DQED) systems, but the large majority of them have been obtained
considering one incoming photon, and within the rotating-wave-approximation, valid for small
couplings between the photon field and the FLS, which conserves the total number of
excitations (be it a photon or an excitation of the FLS). New effects, and perhaps strong
photon-photon interaction mediated by the FLS, are expected when a few photons are launched
into the waveguide. However, the theoretical analysis is this many-body situation is notoriously
difficult and has only been performed for a few cases concerning two and three photons treated
with simplified hamiltonians (as linear photonic dispersion relations in the waveguides and
rotating wave approximation). In this talk we will present a general framework that can address
the full many-body sitiuation where any number of photons in a waveguide interactact with an
arbitrary number of FLS. Our formalism can take into account both the intricacies of non-linear
dispersion relations (and thus the existence of band edges) and the full FLS-field hamiltonian
(including the counter-rotating terms that do not conserve the number of excitations). We will
present results for the few-level dynamics, transmission and resonant fluorescence as a
function of FLS-field coupling, including the so-called ultrastrong coupling regime.
Plasmons on the Atomic Scale: Quantum Theory of Plasmon Eigenmodes
in Nanostructures
Kirsten Andersen[1], Karsten W. Jacobsen, Kristian S. Thygesen
CAMD, Department of Physics, Technical University of Denmark, Lyngby, Denmark
CAMD, Department of Physics, Technical University of Denmark, Lyngby, Denmark
When the size of a plasmonic structure reaches the nano-scale, quantum effects begin to play a
larger role and the widely used classical models of electronic response break down. To explore
the role of these effects on the energy, lifetime, and spatial shape of the plasmons and to
identify the range of validity of the classical models, we have applied linear response
time-dependent density functional theory (TDDFT) to obtain the plasmon eigenmodes of
different types of metallic nanostructures, including 2D structure such as thin films, graphene
and metallic transition metal dichalcogenides. In the case of 1D, we have studied the response
of freestanding metal nanowires and coupled nanowire dimers, and plasmons on the edges of
MoS2 nanoribbons, where we found 1D plasmons with localization on the atomic scale. The
quantum plasmon modes are computed as the eigenstates of the non-local and frequency
dependent dielectric matrix with zero eigenvalues.[1] This method provides a real-space
visualization of the plasmon modes, and includes quantum mechanical effects such as electron
spill-out, quantum confinement, surface scattering, coupling to single-particle transitions, and
non-local response. In general we find that for the plasmons in simple metals, quantum
confinement and the effect of spill out leads to a red shift of the plasmon energies for smaller
structures. This is contradictory to observations for silver nanoparticles where a blue shift was
observed, and indicates the importance of interband transitions for plasmons in noble metals.
Also for plasmons in true 2D and 1D, the presence of interband-transitions can have a big
impact on the resonances, leading to deviation from the ideal metal. For monolayer transition
metal dichalcogenides, this leads to a redshift and damping of the plasmon that stems from a
single metallic band [2]. This behaviour is also observed for the localized 1D plasmon on the
edge of a MoS2 nanoribbon, where screening by transitions within the MoS2 sheet leads to
deviations from ideal 1D result.
[1] K. Andersen, K.W. Jacobsen and K.S. Thygesen, Phys. Rev. B 86, 245129 (2012)
[2] K. Andersen and K.S. Thygesen, Phys. Rev. B 88, 155128 (2013)
Influence of Electron Tunneling in Ultranarrow Plasmonic GAPS
Rubén Esteban[1], J. Aizpurua
Donostia International Physics Center DIPC and Materials Physics Center
CSIC-UPV/EHU,
Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
Donostia International Physics Center DIPC and Materials Physics Center
CSIC-UPV/EHU,
Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
The optical properties of plasmonic systems are often optimized by decreasing the separation
distance between particles. However, as the gaps become subnanometric, the emergence of
electron tunneling strongly modifies the response and can impose constraints to the achievable
performance [1]. In this talk, we present our study of the influence of tunneling for several
scenarios and discuss the importance of the results for spectroscopic measurements and
non-linear processes [2,3]. We also describe the Quantum Corrected Model (QCM) [4], which
allows obtaining the plasmonic response of large structures and analyzing the separate
influence of non-local and tunneling effects. Notably, we apply the QCM to interpret different
recent experimental measurements that reveal this tunneling regime [5,6]. The interaction
between electron transfer and optical properties in subnanometric gaps offers promising
possibilities to study ultrafast and ultraconfined optoelectronic processes.
[1] J. Zuloaga, E. Prodan and P. Nordlander, Nano Letters 9 (2009) 887– 891.
[2] D. C. Marinica, A. K. Kazansky, P. Nordlander, J. Aizpurua and A. G. Borisov, Nano Letters 12 (2012)
1333– 1339.
[3] M. Danckwerts and L. Novotny, PRL 98 (2007) 026104
[4] R. Esteban, A. G. Borisov, P. Nordlander and J. Aizpurua, Nat Commun 3 (2012) 825.
[5] J. A. Scholl, A. García-Etxarri, A. L. Koh and J. A. Dionne, Nano Letters 13 (2013) 564– 569.
[6] K. J. Savage, M. M. Hawkeye, R. Esteban , A. G. Borisov, J. Aizpurua and J. J. Baumberg, Nature
491 (2012) 574– 577.
Inelastic scattering and current-induced forces in nano-conductors
Tue Gunst[1], Mads Brandbyge
Technical University of Denmark, DTU Nanotech, Kgs. Lyngby, Denmark
Technical University of Denmark, DTU Nanotech, Kgs. Lyngby, Denmark
The interplay between electronic current and phonon dynamics is an important and intriguing
problem in nanoelectronics. For instance, this interaction is observed as contact disruption in
graphene nanoconstrictions (GNCs), where the current-density can locally be very high, and is
used for current-annealing of graphene edges [1]. Additionally, the structural response to the
high bias can be studied by in situ transmission electron microscopy, making GNCs a good test
bed for current-induced phenomena [2]. We have studied phonon dynamics in a GNC in the
presence of electronic current using nonequilibrium Green’ s functions (NEGF) and a
semi-classical Langevin equation in combination with density functional theory (DFT)
calculations [3]. We will argue that current-induced forces, different from Joule heating, will
severely heat up such nanostructures. In addition, we examine the inelastic scattering effects in
the electronic current by a recently developed method, that can include the rapid variation in the
electronic spectrum with energy often occurring in molecular and graphene related devices [4].
[1] Qi et al. Nano Lett., 2014, 14 (8), pp 4238– 4244.
[2] F. Börrnert, A. Barreiro, D. Wolf, M. I. Katsnelson, B. Büchner,L. M. K. Vandersypen, M. H. Rümmeli,
Nano Lett. 12, 4455 (2012).
[3] T. Gunst, J.-T. Lü, P. Hedegaard, M. Brandbyge, Phys. Rev. B Rapid Comm. 88, 0161401 (2013).
[4] J.-T. Lü, R. B. Christensen, G. Foti, T. Frederiksen, T. Gunst, M. Brandbyge, Phys. Rev. B Rapid
Comm. 89, 081405 (2014).
Electronic band structure and phonon dispersion relation at the Tl/Si(111)
surface from first principles calculations.
Peio G. Goiricelaya[1], Asier Eiguren [1][2], Idoia G. Gurtubay [1][2]
University of Basque Country (UPV/EHU), Leioa, Spain
[1] University of Basque Country (UPV/EHU), Leioa, Spain
[2] Donostia International Physics Center (DIPC), Donostia, Spain
We present the electronic band structure and phonon dispersion relation of the Tl/Si(111)
surface. Our ab initio calculations have been carried out with and without the spin-orbit
interaction. This surface is a semiconductor with a band gap between electronic surface states
of the order of tenths of eV but The highest occupied surface state has a very large penetration.
Therefore we simulate a semi-infinite crystal considering the Gottlieb method.
Resonance trapping at interfaces
Ulrich Höfer[1]
Fachbereich Physik, Philipps-Universität, 35032 Marburg, Germany
Resonant electron transfer into the bulk is an important and often dominating decay channel for
electronic excitation at surfaces and interfaces. Experimentally such processes can be studied
in a straight forward way by time-resolved two-photon photoemission (2PPE). Examples from
the work of our group are organic/metal or graphene/metal interface states and the topological
surface states of Sb2Te3. In this talk I will show that rather nonintuitive phenomena can occur
as a result of quantum mechanical interference effects. I will present a theoretical description for
the decay dynamics of strongly coupled but energetically close levels at surfaces of simple
metals that leads to the effect of resonance trapping. The calculations explain recently obtained
2PPE data for the image-potential resonances of Al(001). Surprisingly, the theory predicts the
existence of a well resolved series of such states even for situations of infinitely strong coupling
to a jellium-like continuum.Dynamical Study of Electron Transfer in
Alkanethiolate Self-Assembled Monolayers Adsorbed at the Au(111)
Surface
Veronika Prucker[1], Pedro B. Coto [1], Óscar Rubio-Pons [1], Michel Bockstedte [1],
Haobin Wang [2], Michael Thoss [1]
Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
[1] Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
[2] New Mexico State University, Las Cruces, New Mexico, USA
In this contribution, we present a dynamical ab-initio study of electron transfer (ET) in a series of
self-assembled monolayers consisting of nitrile substituted short-chain alcanethiolate molecules
on gold substrates. Employing a model Hamiltonian, which is parametrised by first principles
electronic structure calculations [1], and dynamical simulations, we analyse the main factors
underlying the ET process. In accordance to experiments [2,3], we demonstrate the
dependence of the ET process on the molecular chain length and on the symmetry of the donor
state, which allows to control the electron injection times even in the case of nearly degenerate
donor states [4]. Additionally, we discuss the influence of partly occupied substrate states at
room temperature on the ET process.
[1] I. Kondov et al., J. Phys. Chem. C 111 11970 (2007).
[2] F. Blobner et al., J. Phys. Chem. Lett. 3 436 (2012).
[3] P. Kao et.al., J. Phys. Chem. C 114 13766 (2010).
[4] V. Prucker et al., J. Phys. Chem. C 117 25334 (2013).
4 Posters
Describing Dynamics of Molecules in Intense Laser Fields using
TD-DFT-based Methods
Pablo Lopez[1], P. López-Tarifa1, E. Liberatore1, I. Tavernelli1 and U. Röthlisberger1
École Polytechnique Fédérale de Lausanne SB - ISIC - LCBC, CH-1015 Lausanne,
Switzerland
École Polytechnique Fédérale de Lausanne SB - ISIC - LCBC, CH-1015 Lausanne,
Switzerland
High harmonic spectroscopies have heralded the arrival of attosecond light pulses, and with it
the emergence of a radical new technology that is moving time-resolved spectroscopy and
control techniques from the molecular (femtosecond) to the electronic (attosecond) timescale
[1]. In the process of high harmonic generation (HHG), during each half of the optical cycle, the
oscillating electric field of an intense laser pulse ionizes electrons from atoms, accelerates them
away and then drives them back to re-collide with their parent ion. In each collision, a short
burst of extreme ultraviolet (XUV) photons is created. The information about the molecular
structure and the attosecond electronic dynamics is encoded in the HHG spectra, phases and
polarizations, that need theoretical support to be fully understood. We propose to describe the
electron dynamics occurring in the HHG of oriented molecules [2] using Time-Dependent
Density Functional Theory Molecular Dynamics simulations (TD-DFT MD) [3, 4]. Taking the
iodoacetylene molecule (I-C≡C-H) as a test case, our aim is to rationalize the electronic
movement triggered by the external pulse and monitor the dynamics of the hole created during
the process [5]. For that, we will compare the relaxation of the molecule after a single ionization
from selected molecular orbitals to that occurring in the presence of an external field. We will
show that preliminary results in the relaxation of I-C≡C-H+ generated by ionization from a
HOMO/HOMO-1 superposition of molecular orbitals, result in a good agreement with the
experimentally observed characteristic 2 fs period of electronic oscillations [6].
[1] P. H. Bucksbaum, Nature 421, 593-594 (2003).
[2] P. M. Kraus, A. Rupenyan, and H. J. Wörner, Phys. Rev. Lett. 109, 233903 (2012). [3] I. Tavernelli, U.
F. Röhrig, and U. Rothlisberger, Mol. Phys. 103, 963 (2005).
[4] I. Tavernelli, B. F. E. Curchod, and U. Rothlisberger, Phys. Rev. A 81, 052508 (2010). [5] P. M. Kraus
and H. J. Wörner, private communication.
[6] M. Allan et al., Faraday Trans. 2 73, 1406 (1977).
The influence of U parameter on highly correlated systems: the case of
ABO4 compounds
Mohamed El Amine Moussa[1], Salima Kacimi and Ali Zaoui
Modelling and Simulation in Materials Science Laboratory, Physics Department,
University of Sidi Bel-Abbes, Algeria
We investigated the electronic structure withon-site Coulomb potential for the RE-derived 4f
orbitals and M-derived 3d to obtain the Correct ground state of REMO4. The structural
parameters, density of states and band structures have been given in detail. Our results indicate
that the Fermi level is largely dominated by atom orbitals of vanadate and oxygen ions, but
R-cation influences these electronic states. A detailed analysis shows that the LSDA U Method
provides the better description of the present systems.
Dynamical Study of Electron Transfer in Alkanethiolate Self-Assembled
Monolayers Adsorbed at the Au(111) Surface
Veronika Prucker[1], Pedro B. Coto[1], Óscar Rubio-Pons[1], Michel Bockstedte[1],
Haobin Wang[2], Michael Thoss[1]
[1] Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
[2] New Mexico State University, Las Cruces, New Mexico, USA
In this contribution, we present a dynamical ab-initio study of electron transfer (ET) in a series of
self-assembled monolayers consisting of nitrile substituted short-chain alcanethiolate molecules
on gold substrates. Employing a model Hamiltonian, which is parametrised by first principles
electronic structure calculations [1], and dynamical simulations, we analyse the main factors
underlying the ET process. In accordance to experiments [2,3], we demonstrate the
dependence of the ET process on the molecular chain length and on the symmetry of the donor
state, which allows to control the electron injection times even in the case of nearly degenerate
donor states [4]. Additionally, we discuss the influence of partly occupied substrate states at
room temperature on the ET process.
[1] I. Kondov et. al., J. Phys. Chem. C 111 11970 (2007)
[2] F. Blobner et al., J. Phys. Chem. Lett. 3 436 (2012)
[3] P. Kao et al., J. Phys. Chem. C 114 13766 (2010)
[4] V. Prucker et al., J. Phys. Chem. C 117 25334 (2013)
5 Participant List
Organizers
Díaz, Cristina
Universidad Autónoma de Madrid, Spain
Diaz-Tendero, Sergio
Universidad Autonoma de Madrid, Spain
Feist, Johannes
Universidad Autónoma de Madrid, Spain
Garcia-Vidal, Francisco
Universidad Autonoma de Madrid, Spain
Martin, Fernando
Autonomous University of Madrid, Spain
Aguirre, Nestor - Universidad Autónoma de Madrid, Spain
Alcamí, Manuel - Autonomous University of Madrid, Spain
Andersen, Kirsten - CAMD, department of physics, DTU, Denmark
Arnau, Andrés - EHU-UPV, Spain
B. Coto, Pedro - Institut für Theoretische Physik, Friedrich-Alexander Universtät
Erlangen-Nürnberg, Germany
Cuerda, Javier - Universidad Autónoma de Madrid, Spain
Eiguren, Asier - University of the Basque Country, San Sebastián, Spain
Esteban, Rubén - Donostia International Physics Center, Spain
G. de Gurtubay, Idoia - University of the Basque Country (UPV/EHU), Spain
G. Goiricelaya, Peio - Departamento de Fisica de la Materia Condensada, Facultad
de Ciencia y Tecnologia, University of the Basque Country (UPV/EHU), Spain
Galego, Javier - Universidad Autónoma de Madrid, Spain
Gauyacq, Jean-Pierre - Université de Paris-sud, France
Gunst, Tue - Technical University of Denmark, Lyngby, Denmark
Höfer, Ulrich - Philipps-Universität Marburg, Germany
Hutchison, James A. - Univ. Strasbourg, France
Iturbe, Aitzol - Materia Kondentsatuaren Fisika Saila, Zientzia eta Teknologia
Fakultatea, UPV/EHU, Spain
Kling, Matthias - Max Planck Institute for Quantum Optics, Germany
López Vázquez de Parga, Amadeo - Universidad Autónoma de Madrid, Spain
Lopez, Pablo - Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland
Lorente, Nicolás - Centro de Investigaciones en Nanociencia y Nanotecnologia, Spain
Manfredi, Giovanni - IPCMS - Centre National de la Recherche Scientifique - France,
France
Martín Moreno, Luis - CSIC & Univ. Zaragoza, Spain
Prucker, Veronika - Theoretische Festkoerperphysik, FAU Erlangen-Nuernberg,
Germany
Robledo Relaño, Maitreyi - Universidad Autonoma de Madrid, Spain
Robles, Roberto - ICN-CSIC, Spain
Saalfrank, Peter - University of Potsdam, Germany
Stockman, Mark I. - Georgia State University, USA
Stradi, Daniele - Technical University of Denmark, DTU Nanotech, Denmark
TREMBLAY, Jean Christophe - Institute of Chemistry and Biochemistry, Freie
Universität Berlin, Germany
Vogelgesang, Ralf - Oldenburg University, Germany