2,889 research outputs found
Electric-Field-Induced Resonant Spin Polarization in a Two-Dimensional Electron Gas
Electric response of spin polarization in two-dimensional electron gas with
structural inversion asymmetry subjected to a magnetic field was studied by
means of the linear and non-linear theory and numerical simulation with the
disorder effect. It was found by Kubo linear reponse theory that an electric
resonant response of spin polarization occurs when the Fermi surface is located
near the crossing of two Landau levels, which is induced from the competition
between the spin-orbit coupling and Zeeman splitting. The scaling behavior was
investigated with a simplified two-level model by non-linear method, and the
resonant peak value is reciprocally proportional to the electric field at low
temperatures and to temperature for finite electric fields. Finally numerical
simulation illustrated that impurity potential opens an enegy gap near the
resonant point and suppresses the effect gradually with the increasing strength
of disorder. This resonant effect may provide an efficient way to control spin
polarization by an external electric field.Comment: 6 pages, 5 figure
Theory for electric dipole superconductivity with an application for bilayer excitons
Exciton superfluid is a macroscopic quantum phenomenon in which large
quantities of excitons undergo the Bose-Einstein condensation. Recently,
exciton superfluid has been widely studied in various bilayer systems. However,
experimental measurements only provide indirect evidence for the existence of
exciton superfluid. In this article, by viewing the exciton in a bilayer system
as an electric dipole, we provide a general theory for the electric dipole
superconductivity, and derive the London-type and Ginzburg-Landau-type
equations for the electric dipole superconductors. By using these equations, we
discover the Meissner-type effect and the electric dipole current Josephson
effect. These effects can provide direct evidence for the formation of the
exciton superfluid state in bilayer systems and pave new ways to drive an
electric dipole current.Comment: 10 pages, 5 figures, 1 Supplementary Informatio
Orbital Kondo effect in a parallel double quantum dot
We construct a theoretical model to study the orbital Kondo effect in a
parallel double quantum dot (DQD). Recently, pseudospin-resolved transport
spectroscopy of the orbital Kondo effect in a DQD has been experimentally
reported. The experiment revealed that when interdot tunneling is ignored,
there exist two and one Kondo peaks in the conductance-bias curve for the
pseudospin-non-resolved and pseudospin-resolved cases, respectively. Our
theoretical studies reproduce this experimental result. We also investigate the
situation of all lead voltages being non-equal (the complete
pseudospin-resolved case), and find that there are four Kondo peaks at most in
the curve of the conductance versus the pseudospin splitting energy. When the
interdot tunneling is introduced, some new Kondo peaks and dips can emerge.
Besides, the pseudospin transport and the pseudospin flipping current are also
studied in the DQD system. Since the pseudospin transport is much easier to be
controlled and measured than the real spin transport, it can be used to study
the physical phenomenon related to the spin transport.Comment: 18 pages, 7 figures, accepted by J. Phys.: Condens. Matter in
September 201
Equations of motion of test particles for solving the spin-dependent Boltzmann-Vlasov equation
A consistent derivation of the equations of motion (EOMs) of test particles
for solving the spin-dependent Boltzmann-Vlasov equation is presented. The
resulting EOMs in phase space are similar to the canonical equations in
Hamiltonian dynamics, and the EOM of spin is the same as that in the Heisenburg
picture of quantum mechanics. Considering further the quantum nature of spin
and choosing the direction of total angular momentum in heavy-ion reactions as
a reference of measuring nucleon spin, the EOMs of spin-up and spin-down
nucleons are given separately. The key elements affecting the spin dynamics in
heavy-ion collisions are identified. The resulting EOMs provide a solid
foundation for using the test-particle approach in studying spin dynamics in
heavy-ion collisions at intermediate energies. Future comparisons of model
simulations with experimental data will help constrain the poorly known
in-medium nucleon spin-orbit coupling relevant for understanding properties of
rare isotopes and their astrophysical impacts.Comment: 5 page
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