383 research outputs found
Transport properties of a two-dimensional electron liquid at high magnetic field
The chiral Luttinger liquid model for the edge dynamics of a two-dimensional
electron gas in a strong magnetic field is derived from coarse-graining and a
lowest Landau level projection procedure at arbitrary filling factors
-- without reference to the quantum Hall effect. Based on this model, we
develop a formalism to calculate the Landauer-B\"uttiker conductances in
generic experimental set-ups including multiple leads and voltage probes. In
the absence of tunneling between the edges the "ideal" Hall conductances
( if lead is immediately upstream of lead ,
and otherwise) are recovered. Tunneling of quasiparticles of
fractional charge between different edges is then included as an
additional term in the Hamiltonian. In the limit of weak tunneling we obtain
explicit expressions for the corrections to the ideal conductances. As an
illustration of the formalism we compute the current- and temperature-dependent
resistance of a quantum point contact localized at the center of
a gate-induced constriction in a quantum Hall bar. The exponent in the
low-current relation shows a nontrivial
dependence on the strength of the inter-edge interaction, and its value changes
as , where is the Hall voltage, falls below
a characteristic crossover energy , where is the edge
wave velocity and is the length of the constriction. The consequences of
this crossover are discussed vis-a-vis recent experiments in the weak tunneling
regime.Comment: 20 pages, 8 figures, Revtex4, adjourned with referee's comments,
added references and typos correcte
Resonant Andreev Tunneling in Strongly Interacting Quantum Dots
We study resonant Andreev tunneling through a strongly interacting quantum
dot connected to a normal and to a superconducting lead. We obtain a formula
for the Andreev current and apply it to discuss the linear and non-linear
transport in the nonperturbative regime, where the effects of the Kondo
resonance on the two particle tunneling arise. In particular we notice an
enhancement of the Kondo anomaly in the characteristics due to the
superconducting electrode.Comment: 13 pages Revtex, 3 figures .p
Spin Hall effects due to phonon skew scattering
A diversity of spin Hall effects in metallic systems is known to rely on Mott
skew scattering. In this work its high-temperature counterpart, phonon skew
scattering, which is expected to be of foremost experimental relevance, is
investigated. In particular, the phonon skew scattering spin Hall conductivity
is found to be practically -independent for temperatures above the Debye
temperature . As a consequence, in Rashba-like systems a high- linear
behavior of the spin Hall angle demonstrates the dominance of extrinsic
spin-orbit scattering only if the intrinsic spin splitting is smaller than the
temperature.Comment: Accepted version, 4 (+1) pages, 2 figure
Quantum noise in the spin transfer torque effect
Describing the microscopic details of the interaction of magnets and
spin-polarized currents is key to achieve control of such systems at the
microscopic level. Here we discuss a description based on the Keldysh
technique, casting the problem in the language of open quantum systems. We
reveal the origin of noise in the presence of both field-like and damping like
terms in the equation of motion arising from spin conductance
Nonlinear Inverse Spin Galvanic Effect in Anisotropic Disorder-free Systems
Spin transport phenomena in solid materials suffer limitations from spin
relaxation associated to disorder or lack of translational invariance.
Ultracold atoms, free of that disorder, can provide a platform to observe
phenomena beyond the usual two-dimensional electron gas. By generalizing the
approach used for isotropic two-dimensional electron gases, we theoretically
investigate the inverse spin galvanic effect in the two-level atomic system in
the presence of anisotropic Rashba-Dresselhaus spin-orbit couplings (SOC) and
external magnetic field. We show that the combination of the SOC results in an
asymmetric case: the total spin polarization considered for a small momentum
has a longer spin state than in a two-dimensional electron gas when the SOC
field prevails over the external electric field. Our results can be relevant
for advancing experimental and theoretical investigations in spin dynamics as a
basic approach for studying spin state control
Specific Heat Anomaly and Adiabatic Hysteresis in Disordered Electron Systems in a Magnetic Field
We consider the thermodynamic behavior of a disordered interacting electron
system in two dimensions. We show that the corrections to the thermodynamic
potential in the weakly localized regime give rise to a non monotonic behavior
of the specific heat both in temperature and magnetic field. From this effect
we predict the appearance of adiabatic hysteresis in the magnetoconductance.
Our results can be interpreted as precursor effect of formation of local
moments in disordered electron systems. We also comment on the relevance of our
analysis in three dimensional systems.Comment: 4 pages, RevTeX, 3 figures, accepted by EPJ
Theory of charge-spin conversion at oxide interfaces: The inverse spin-galvanic effect
We evaluate the non-equilibrium spin polarization induced by an applied
electric field for a tight-binding model of electron states at oxides
interfaces in LAO/STO heterostructures. By a combination of analytic and
numerical approaches we investigate how the spin texture of the electron
eigenstates due to the interplay of spin-orbit coupling and inversion asymmetry
determines the sign of the induced spin polarization as a function of the
chemical potential or band filling, both in the absence and presence of local
disorder. With the latter, we find that the induced spin polarization evolves
from a non monotonous behavior at zero temperature to a monotonous one at
higher temperature. Our results may provide a sound framework for the
interpretation of recent experiments.Comment: Submitted to Proceedings of SPIE Nanoscience + Engineering 2018,
Spintronics XI, 23 pages, 9 figure
Intrinsic spin Hall effect in systems with striped spin-orbit coupling
The Rashba spin-orbit coupling arising from structure inversion asymmetry
couples spin and momentum degrees of freedom providing a suitable (and very
intensively investigated) environment for spintronic effects and devices. Here
we show that in the presence of strong disorder, non-homogeneity in the
spin-orbit coupling gives rise to a finite spin Hall conductivity in contrast
with the corresponding case of a homogeneous linear spin-orbit coupling. In
particular, we examine the inhomogeneity arising from a striped structure for a
two-dimensional electron gas, affecting both density and Rashba spin-orbit
coupling. We suggest that this situation can be realized at oxide interfaces
with periodic top gating.Comment: 9 pages, 8 figure
Electronic thermal conductivity of disordered metals
We calculate the thermal conductivity of interacting electrons in disordered
metals. In our analysis we point out that the interaction affects thermal
transport through two distinct mechanims, associated with quantum interference
corrections and energy exchange of the quasi particles with the electromagnetic
environment, respectively. The latter is seen to lead to a violation of the
Wiedemann-Franz law. Our theory predicts a strong enhancement of the Lorenz
ratio over the value which is predicted by the
Wiedemann-Franz law, when the electrons encounter a large environmental
impedance.Comment: 4 page
Quasiclassical approach and spin-orbit coupling
We discuss the quasiclassical Green function method for a two-dimensional
electron gas in the presence of spin-orbit coupling, with emphasis on the
meaning of the -integration procedure. As an application of our approach,
we demonstrate how the spin-Hall conductivity, in the presence of spin-flip
scattering, can be easily obtained from the spin-density continuity equation.Comment: 3 pages, Submitted to Physica
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