46 research outputs found
Spin-Hall effect on edge magnetization and electric conductance of a 2D semiconductor strip
The intrinsic spin-Hall effect on spin accumulation and electric conductance
in a diffusive regime of a 2D electron gas has been studied for a 2D strip of a
finite width. It is shown that the spin polarization near the flanks of the
strip, as well as the electric current in the longitudinal direction exhibit
damped oscillations as a function of the width and strength of the Dresselhaus
spin-orbit interaction. Cubic terms of this interaction are crucial for spin
accumulation near the edges. As expected, no effect on the spin accumulation
and electric conductance have been found in case of Rashba spin-orbit
interaction.Comment: 4 pages, 1 figure, some changes in the tex
Waveguide diffusion modes and slowdown of D'yakonov-Perel' spin relaxation in narrow 2-D semiconductor channels
We have shown that in narrow 2D semiconductor channels the D'yakonov-Perel'
spin relaxation rate is strongly reduced. This relaxation slowdown appears in
special waveguide diffusion modes which determine the propagation of spin
density in long channels. Experiments are suggested to detect the theoretically
predicted effects. A possible application is a field effect transistor operated
with injected spin current.Comment: 4 page
DC Spin Current Generation in a Rashba-type Quantum Channel
We propose and demonstrate theoretically that resonant inelastic scattering
(RIS) can play an important role in dc spin current generation. The RIS makes
it possible to generate dc spin current via a simple gate configuration: a
single finger-gate that locates atop and orients transversely to a quantum
channel in the presence of Rashba spin-orbit interaction. The ac biased
finger-gate gives rise to a time-variation in the Rashba coupling parameter,
which causes spin-resolved RIS, and subsequently contributes to the dc spin
current. The spin current depends on both the static and the dynamic parts in
the Rashba coupling parameter, and , respectively, and is
proportional to . The proposed gate configuration has the
added advantage that no dc charge current is generated. Our study also shows
that the spin current generation can be enhanced significantly in a double
finger-gate configuration.Comment: 4 pages,4 figure
Spin-Hall conductivity of a disordered 2D electron gas with Dresselhaus spin-orbit interaction
The spin-Hall conductivity of a disordered 2D electron gas has been
calculated for an arbitrary spin-orbit interaction. We have found that in the
diffusive regime of electron transport, in accordance with previous
calculations, the dc spin-Hall conductivity of a homogeneous system turns to
zero due to impurity scattering when the spin-orbit coupling is represented
only by the Rashba interaction. However, when the Dresselhaus interaction is
taken into account, the spin-Hall current is not zero. We also considered the
spin-Hall currents induced by an inhomogeneous electric field. It is shown that
a time dependent electric charge induces a vortex of spin-Hall currents.Comment: 5 pages, figure adde
The effect of the spin-orbit geometric phase on the spectrum of Aharonov-Bohm oscillations in a semiconductor mesoscopic ring
Taking into account the spin precession caused by the spin-orbit splitting of
the conduction band in semiconductor quantum wells, we have calculated the
Fourier spectra of conductance and state-density correlators in a 2D ring, in
order to investigate the structure of the main peak corresponding to
Aharonov-Bohm oscillations. In narrow rings the peak structure is determined by
the competition between the spin-orbit and the Zeeman couplings. The latter
leads to a peak broadening, and produces the peak splitting in the
state-density Fourier spectrum. We have found an oscillation of the peak
intensity as a function of the spin-orbit coupling constant, and this effect of
the quantum interference caused by the spin geometric phase is destroyed with
increasing Zeeman coupling.Comment: 4 pages, 3 figures, uses epsfig.st
Sum rules for spin-Hall conductivity cancelation
It has been shown recently that the universal dc spin conductivity of
two-dimensional electrons with a Rashba spin-orbit interaction is canceled by
vertex corrections in a weak scattering regime. We prove that the zero bulk
spin conductivity is an intrinsic property of the free-electron Hamiltonian and
scattering is merely a tool to reveal this property in terms of the
diagrammatic technique. When Zeeman energy is neglected, the zero dc
conductivity persists in a magnetic field. Spin conductivity increases
resonantly at the cyclotron frequency and then decays towards the universal
value.Comment: 4 pages, 1 figur
AC Josephson Effect Induced by Spin Injection
Pure spin currents can be injected and detected in conductors via
ferromagnetic contacts. We consider the case when the conductors become
superconducting. A DC pure spin current flowing in one superconducting wire
towards another superconductor via a ferromagnet contact induces AC voltage
oscillations caused by Josephson tunneling of condensate electrons.
Quasiparticles simultaneously counterflow resulting in zero total electric
current through the contact. The Josephson oscillations can be accompanied by
Carlson-Goldman collective modes leading to a resonance in the voltage
oscillation amplitude.Comment: 5 page
Superconductivity in charge Kondo systems
We present a theory of superconductivity in charge Kondo systems, materials
with resonant quantum valence fluctuations, in the regime where the transition
temperature is comparable to the charge Kondo resonance. We find
superconductivity induced by charge Kondo impurities, study how pairing of a
superconducting host is enhanced due to charge Kondo centers and investigate
the interplay between Kondo-scattering and inter-impurity Josephson coupling.
We discuss the implications of our theory for Tl-doped PbTe, which has recently
been identified as a candidate charge Kondo system.Comment: 4 pages, 4 figures; revised version; detailed discussion on the
physics of Tl-doped PbTe adde
Optoelectric spin injection in semiconductor heterostructures without ferromagnet
We have shown that electron spin density can be generated by a dc current
flowing across a junction with an embedded asymmetric quantum well. Spin
polarization is created in the quantum well by radiative electron-hole
recombination when the conduction electron momentum distribution is shifted
with respect to the momentum distribution of holes in the spin split valence
subbands. Spin current appears when the spin polarization is injected from the
quantum well into the -doped region of the junction. The accompanied
emission of circularly polarized light from the quantum well can serve as a
spin polarization detector.Comment: 2 figure
Aharonov-Casher oscillations of spin current through a multichannel mesoscopic ring
The Aharonov-Casher (AC) oscillations of spin current through a 2D ballistic
ring in the presence of Rashba spin-orbit interaction and external magnetic
field has been calculated using the semiclassical path integral method. For
classically chaotic trajectories the Fokker-Planck equation determining
dynamics of the particle spin polarization has been derived. On the basis of
this equation an analytic expression for the spin conductance has been obtained
taking into account a finite width of the ring arms carrying large number of
conducting channels. It was shown that the finite width results in a broadening
and damping of spin current AC oscillations. We found that an external magnetic
field leads to appearance of new nondiagonal components of the spin
conductance, allowing thus by applying a rather weak magnetic field to change a
direction of the transmitted spin current polarization.Comment: 16 pages, 6 figure