217 research outputs found
Universal Equilibrium Currents in the Quantum Hall Fluid
The equilibrium current distribution in a quantum Hall fluid that is
subjected to a slowly varying confining potential is shown to generally consist
of strips or channels of current, which alternate in direction, and which have
universal integrated strengths. A measurement of these currents would yield
direct independent measurements of the proper quasiparticle and quasihole
energies in the fractional quantum Hall states.Comment: 4 pages, Revte
Effect of electrical bias on spin transport across a magnetic domain wall
We present a theory of the current-voltage characteristics of a magnetic
domain wall between two highly spin-polarized materials, which takes into
account the effect of the electrical bias on the spin-flip probability of an
electron crossing the wall. We show that increasing the voltage reduces the
spin-flip rate, and is therefore equivalent to reducing the width of the domain
wall. As an application, we show that this effect widens the temperature window
in which the operation of a unipolar spin diode is nearly ideal.Comment: 11 pages, 3 figure
Exact exchange-correlation potential for a time-dependent two electron system
We obtain an exact solution of the time-dependent Schroedinger equation for a
two-electron system confined to a plane by an isotropic parabolic potential
whose curvature is periodically modulated in time. From this solution we
compute the exact time-dependent exchange correlation potential v_xc which
enters the Kohn-Sham equation of time-dependent density functional theory. Our
exact result provides a benchmark against which various approximate forms for
v_xc can be compared. Finally v_xc is separated in an adiabatic and a pure
dynamical part and it is shown that, for the particular system studied, the
dynamical part is negligible.Comment: 23 pages, 6 figure
Local exchange-correlation vector potential with memory in Time-Dependent Density Functional Theory: the generalized hydrodynamics approach
Using Landau Fermi liquid theory we derive a nonlinear non-adiabatic
approximation for the exchange-correlation (xc) vector potential defined by the
xc stress tensor. The stress tensor is a local nonlinear functional of two
basic variables - the displacement vector and the second-rank tensor which
describes the evolution of momentum in a local frame moving with Eulerian
velocity. For irrotational motion and equilibrium initial state the dependence
on the tensor variable reduces to that on a metrics generated by a dynamical
deformation of the system.Comment: RevTex, 5 pages, no figures. Final version published in PR
Correlation effects and the high-frequency spin susceptibility of an electron liquid: Exact limits
Spin correlations in an interacting electron liquid are studied in the
high-frequency limit and in both two and three dimensions. The third-moment sum
rule is evaluated and used to derive exact limiting forms (at both long- and
short-wavelengths) for the spin-antisymmetric local-field factor, . In two dimensions is found to diverge as at long wavelengths,
and the spin-antisymmetric exchange-correlation kernel of time-dependent spin
density functional theory diverges as in both two and three dimensions.
These signal a failure of the local-density approximation, one that can be
redressed by alternative approaches.Comment: 5 page
Many-body effective mass enhancement in a two-dimensional electron liquid
Motivated by a large number of recent magnetotransport studies we have
revisited the problem of the microscopic calculation of the quasiparticle
effective mass in a paramagnetic two-dimensional (2D) electron liquid (EL). Our
systematic study is based on a generalized approximation which makes use
of the many-body local fields and takes advantage of the results of the most
recent QMC calculations of the static charge- and spin-response of the 2D EL.
We report extensive calculations for the many-body effective mass enhancement
over a broad range of electron densities. In this respect we critically examine
the relative merits of the on-shell approximation, commonly used in
weak-coupling situations, {\it versus} the actual self-consistent solution of
the Dyson equation. We show that already for and higher, a
solution of the Dyson equation proves here necessary in order to obtain a well
behaved effective mass. Finally we also show that our theoretical results for a
quasi-2D EL, free of any adjustable fitting parameters, are in good qualitative
agreement with some recent measurements in a GaAs/AlGaAs heterostructure.Comment: 12 pages, 3 figures, CMT28 Conference Proceedings, work related to
cond-mat/041226
Spin Hall Drag
We predict a new effect in electronic bilayers: the {\it Spin Hall Drag}. The
effect consists in the generation of spin accumulation across one layer by an
electric current along the other layer. It arises from the combined action of
spin-orbit and Coulomb interactions. Our theoretical analysis, based on the
Boltzmann equation formalism, identifies two main contributions to the spin
Hall drag resistivity: the side-jump contribution, which dominates at low
temperature, going as , and the skew-scattering contribution, which is
proportional to . The induced spin accumulation is large enough to be
detected in optical rotation experiments.Comment: 5 pages, 2 figure
Time-dependent density functional theory beyond the adiabatic local density approximation
In the current density functional theory of linear and nonlinear
time-dependent phenomena, the treatment of exchange and correlation beyond the
level of the adiabatic local density approximation is shown to lead to the
appearance of viscoelastic stresses in the electron fluid. Complex and
frequency-dependent viscosity/elasticity coefficients are microscopically
derived and expressed in terms of properties of the homogeneous electron gas.
As a first consequence of this formalism, we provide an explicit formula for
the linewidths of collective excitations in electronic systems.Comment: RevTeX, 4 page
Gauge-Invariant Formulation of Spin-Current-Density Functional Theory
Spin-currents and non-abelian gauge potentials in electronic systems can be
treated by spin-current-density functional theory, whose main input is the
exchange-correlation (xc) energy expressed as a functional of spin-currents.
Constructing a functional of spin currents that is invariant under
U(1)SU(2) transformations is a long-standing challenge. We solve the
problem by expressing the energy as a functional of a new variable we call
"invariant vorticity". As an illustration we construct the xc energy functional
for a two-dimensional electron gas with linear spin-orbit coupling and show
that it is proportional to the fourth power of the spin current.Comment: 8 pages, 3 figures, submitte
Coulomb-induced Rashba spin-orbit coupling in semiconductor quantum wells
In the absence of an external field, the Rashba spin-orbit interaction (SOI)
in a two-dimensional electron gas in a semiconductor quantum well arises
entirely from the screened electrostatic potential of ionized donors. We adjust
the wave functions of a quantum well so that electrons occupying the first
(lowest) subband conserve their spin projection along the growth axis (Sz),
while the electrons occupying the second subband precess due to Rashba SOI.
Such a specially designed quantum well may be used as a spin relaxation
trigger: electrons conserve Sz when the applied voltage (or current) is lower
than a certain threshold V*; higher voltage switches on the Dyakonov-Perel spin
relaxation.Comment: 4+ pages, 6 figure
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