Download Authors:Qing Jie, Rongwei Hu, Emil Bozin, A

Electronic thermoelectric power factor and
metal-insulator transition in FeSb2
Authors:Qing Jie, Rongwei Hu, Emil Bozin, A. Llobet, I. Zaliznyak, C. Petrovic, Q. Li
(Submitted on 11 Oct 2012)
Abstract: We show that synthesis-induced Metal -Insulator transition (MIT) for electronic transport
along the orthorombic c axis of FeSb$_{2}$ single crystals has greatly enhanced electrical conductivity
while keeping the thermopower at a relatively high level. By this means, the thermoelectric power
factor is enhanced to a new record high S$^{2}$$\sigma$ $\sim$ 8000 $\mu$WK$^{-2}$cm$^{-1}$ at 28
K. We find that the large thermopower in FeSb$_{2}$ can be rationalized within the correlated electron
model with two bands having large quasiparaticle disparity, whereas MIT is induced by subtle structural
differences. The results in this work testify that correlated electrons can produce extreme power factor
values.
Comments:
7 pages, 6 figures
Subjects:
Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci)
Journal reference: Phys. Rev. B 86, 115121 (2012)
DOI:
10.1103/PhysRevB.86.115121
Cite as:
arXiv:1210.3355 [cond-mat.str-el]
(or arXiv:1210.3355v1 [cond-mat.str-el] for this version)
Pseudogap state from quantum criticality
Authors:K. B. Efetov, H. Meier, C. Pépin
(Submitted on 11 Oct 2012)
Abstract: Upon application of an external tuning parameter, a magnetic state can be driven to a normal
metal state at zero temperature. This phenomenon is known as quantum criticality and leads to
fascinating responses in thermodynamics and transport of the compound. In the standard picture, a
single quantum critical point occurs at zero temperature, which results in a nontrivial critical behaviour
in its vicinity. Here we show that in two dimensions the scenario is considerably more complex due to
the enormous amount of quantum fluctuations. Instead of the single point separating the
antiferromagnet from the normal metal, we have discovered a broad region between these two phases
where the magnetic order is destroyed but certain areas of the Fermi surface are closed by a large gap.
This gap reflects the formation of a novel quantum state characterised by a superposition of d-wave
superconductivity and a quadrupole-density wave, id est a state in which an electron quadrupole
density spatially oscillates with a period drastically different from the one of the original spin-density
wave. At moderate temperatures both orders co-exist at short distances but thermal fluctuations
destroy the long-range order. Below a critical temperature the fluctuations are less essential and
superconductivity becomes stable. This new phenomenon may shed some light on the origin of the
mysterious pseudogap state and of the high-temperature transition into the superconducting state in
cuprates. Our results demonstrate that quantum phase transitions between antiferromagnets and
normal metals in layered materials may be the proper playground for search of new high temperature
superconductors.
Comments: 32 pages, 12 figures
Subjects:
Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con)
Cite as:
arXiv:1210.3276 [cond-mat.str-el]
(or arXiv:1210.3276v1 [cond-mat.str-el] for this version)
Field-induced magnetic behavior in quasione-dimensional Ising-like antiferromagnet
BaCo2V2O8: a detailed single-crystal
neutron diffraction study
Authors:E. Canévet, B. Grenier, M. Klanjšek, C. Berthier, M. Horvatić, V. Simonet, P. Lejay
(Submitted on 11 Oct 2012)
Abstract: BaCo2V2O8 is a nice example of a quasi-one-dimensional quantum spin system that can be
described in terms of Tomonaga-Luttinger liquid physics. This is explored in the present study where the
magnetic field-temperature phase diagram is thoroughly established up to 12 T using single-crystal
neutron diffraction. The transition from the N\'eel phase to the incommensurate longitudinal spin
density wave (LSDW) phase through a first-order transition, as well as the critical exponents associated
with the paramagnetic to ordered phase transitions, and the magnetic order both in the N\'eel and in
the LSDW phase are determined, thus providing a stringent test for the theory.
Comments: 16 pages with 15 figures
Subjects:
Strongly Correlated Electrons (cond-mat.str-el)
Cite as:
arXiv:1210.3253 [cond-mat.str-el]
(or arXiv:1210.3253v1 [cond-mat.str-el] for this version)
Signatures of topological phase transitions in
mesoscopic superconducting rings
Authors:Falko Pientka, Alessandro Romito, Mathias Duckheim, Yuval Oreg, Felix von Oppen
(Submitted on 11 Oct 2012)
Abstract: We investigate Josephson currents in mesoscopic rings with a weak link which are in or near a
topological superconducting phase. As a paradigmatic example, we consider the Kitaev model of a
spinless p-wave superconductor in one dimension, emphasizing how this model emerges from more
realistic settings based on semiconductor nanowires. We show that the flux periodicity of the Josephson
current provides signatures of the topological phase transition and the emergence of Majorana fermions
situated on both sides of the weak link even when fermion parity is not a good quantum number. In
large rings, the Majorana fermions hybridize only across the weak link. In this case, the Josephson
current is h/e periodic in the flux threading the loop when fermion parity is a good quantum number but
reverts to the more conventional h/2e periodicity in the presence of fermion-parity changing relaxation
processes. In mesoscopic rings, the Majorana fermions also hybridize through their overlap in the
interior of the superconducting ring. We find that in the topological superconducting phase, this gives
rise to an h/e-periodic contribution even when fermion parity is not conserved and that this
contribution exhibits a peak near the topological phase transition. This signature of the topological
phase transition is robust to the effects of disorder. As a byproduct, we find that close to the topological
phase transition, disorder drives the system deeper into the topological phase. This is in stark contrast
to the known behavior far from the phase transition, where disorder tends to suppress the topological
phase.
Comments: 14 pages, 16 figures
Subjects:
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Cite as:
arXiv:1210.3237 [cond-mat.mes-hall]
(or arXiv:1210.3237v1 [cond-mat.mes-hall] for this version)
Emergent Supersymmetric Many-Body
Systems in Doped Z2 Topological Spin Liquid
of the Toric-Code Model
Authors:Jing He, Jing Yu, Xing-Hai Zhang, Su-Peng Kou
(Submitted on 11 Oct 2012)
Abstract: In this paper, we studied the doped Z2 topological spin liquid of the toric-code model. We
found that the doped holes become supersymmetric particles. The ground state of the doped Z2
topological spin liquid becomes new matters of quantum states - supersymmetric Bose-Einstein
condensation or supersymmetric superfluid. As a result, this system provides a unique example of
manipulatable supersymmetric many-body system.
Comments: 4.5 pages, 3 figures
Subjects:
Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
Cite as:
arXiv:1210.3232 [cond-mat.str-el]
(or arXiv:1210.3232v1 [cond-mat.str-el] for this version)
Spin Hall Effect
Authors:M.I. Dyakonov
(Submitted on 11 Oct 2012)
Abstract: This is a brief review of the phenomenology of the spin Hall effect and related phenomena.
Comments:
12 pages, 4 figures
Subjects:
Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Atomic Physics (physics.atomph); Quantum Physics (quant-ph)
Journal
reference:
Future Trends in Microelectronics, S. Luryi, J. Xu, and A. Zaslavsky (eds), Wiley 2010, p.
251
Cite as:
arXiv:1210.3200 [cond-mat.mes-hall]
(or arXiv:1210.3200v1 [cond-mat.mes-hall] for this version)
Sweeping reciprocal vortex lattice across the
Fermi surface: A new magnetoquantum
oscillations effect in the superconducting
state
Authors:T. Maniv, V. Zhuravlev
(Submitted on 11 Oct 2012)
Abstract: It is shown that coherent scatterings by an ordered vortex lattice are critically enhanced for
quasi particles moving in cyclotron orbits on the Fermi surface through vortex core regions, thus
generating significant quasi-periodic oscillating contributions to the SC free energy as a function of the
inverse magnetic field. The mean frequency of the oscillation provides a fingerprint of the vortex lattice
geometry. Vortex-lattice disorder, tends to suppress this oscillatory component.
Comments: 4 pages, 2 figures, presented on RHMF12
Subjects:
Superconductivity (cond-mat.supr-con)
Cite as:
arXiv:1210.3172 [cond-mat.supr-con]
(or arXiv:1210.3172v1 [cond-mat.supr-con] for this version)
Pseudogap-related charge dynamics in
layered-nickelate R2-xSrxNiO4 (x sim 1)
Authors:M. Uchida, Y. Yamasaki, Y. Kaneko, K. Ishizaka, J. Okamoto, H. Nakao, Y. Murakami, Y. Tokura
(Submitted on 11 Oct 2012)
Abstract: Charge dynamics and its critical behavior are investigated near the metal-insulator transition
of layered-nickelate R2-xSrxNiO4 (R=Nd, Eu). The polarized x-ray absorption spectroscopy experiment
clearly shows the multi-orbital nature which enables the x2-y2-orbital-based checkerboard-type charge
ordering or correlation to persist up to the critical doping region (x sim 1). In the barely metallic region
proximate to the charge-ordered insulating phase, the nominal carrier density estimated from the Hall
coefficient markedly decreases in accord with development of the pseudogap structure in the optical
conductivity spectrum, while the effective mass is least enhanced. The present findings combined with
the results of recent angle-resolved photoemission spectroscopy show that the pseudogap in the metalinsulator critical state evolves due to the checkerboard-type charge correlation to extinguish the
coherent-motion carriers in a characteristic momentum (k)-dependent manner with lowering
temperature.
Comments: 7 pages, 6 figures. Accepted in Physical Review B
Subjects:
Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci)
Cite as:
arXiv:1210.3093 [cond-mat.str-el]
(or arXiv:1210.3093v1 [cond-mat.str-el] for this version)