377 research outputs found
Spin-density induced by electromagnetic wave in two-dimensional electron gas
We consider the magnetic response of a two-dimensional electron gas (2DEG)
with a spin-orbit interaction to a long-wave-length electromagnetic excitation.
We observe that the transverse electric field creates spin polarization
perpendicular to the 2DEG plane. The effect is more prominent in clean systems
with resolved spin-orbit-split subbands, and reaches maximum when the frequency
of the wave matches the subband splitting at the Fermi momentum. The relation
of this effect to the spin-Hall effect is discussed.Comment: Final published for
Drift-diffusion model for spin-polarized transport in a non-degenerate 2DEG controlled by a spin-orbit interaction
We apply the Wigner function formalism to derive drift-diffusion transport
equations for spin-polarized electrons in a III-V semiconductor single quantum
well. Electron spin dynamics is controlled by the linear in momentum spin-orbit
interaction. In a studied transport regime an electron momentum scattering rate
is appreciably faster than spin dynamics. A set of transport equations is
defined in terms of a particle density, spin density, and respective fluxes.
The developed model allows studying of coherent dynamics of a non-equilibrium
spin polarization. As an example, we consider a stationary transport regime for
a heterostructure grown along the (0, 0, 1) crystallographic direction. Due to
the interplay of the Rashba and Dresselhaus spin-orbit terms spin dynamics
strongly depends on a transport direction. The model is consistent with results
of pulse-probe measurement of spin coherence in strained semiconductor layers.
It can be useful for studying properties of spin-polarized transport and
modeling of spintronic devices operating in the diffusive transport regime.Comment: 16 pages, 3 figure
Spin polarizations and spin Hall currents in a two-dimensional electron gas with magnetic impurities
We consider a two-dimensional electron gas in the presence of Rashba
spin-orbit coupling, and study the effects of magnetic s-wave impurities and
long-range non-magnetic disorder on the spin-charge dynamics of the system. We
focus on voltage induced spin polarizations and their relation to spin Hall
currents. Our results are obtained using the quasiclassical Green function
technique, and hold in the full range of the disorder parameter .Comment: 5 pages, 2 figures. References added, minor stylistic modification
Spin diffusion/transport in -type GaAs quantum wells
The spin diffusion/transport in -type (001) GaAs quantum well at high
temperatures ( K) is studied by setting up and numerically solving the
kinetic spin Bloch equations together with the Poisson equation
self-consistently. All the scattering, especially the electron-electron Coulomb
scattering, is explicitly included and solved in the theory. This enables us to
study the system far away from the equilibrium, such as the hot-electron effect
induced by the external electric field parallel to the quantum well. We find
that the spin polarization/coherence oscillates along the transport direction
even when there is no external magnetic field. We show that when the scattering
is strong enough, electron spins with different momentums oscillate in the same
phase which leads to equal transversal spin injection length and ensemble
transversal injection length. It is also shown that the intrinsic scattering is
already strong enough for such a phenomena. The oscillation period is almost
independent on the external electric field which is in agreement with the
latest experiment in bulk system at very low temperature [Europhys. Lett. {\bf
75}, 597 (2006)]. The spin relaxation/dephasing along the diffusion/transport
can be well understood by the inhomogeneous broadening, which is caused by the
momentum-dependent diffusion and the spin-orbit coupling, and the scattering.
The scattering, temperature, quantum well width and external magnetic/electric
field dependence of the spin diffusion is studied in detail.Comment: 12 pages, 6 figures, to be published in J Appl. Phy
Imaging mesoscopic spin Hall flow: Spatial distribution of local spin currents and spin densities in and out of multiterminal spin-orbit coupled semiconductor nanostructures
We introduce the concept of bond spin current, which describes the spin
transport between two sites of the lattice model of a multiterminal spin-orbit
(SO) coupled semiconductor nanostructure, and express it in terms of the
spin-dependent nonequilibrium (Landauer-Keldysh) Green functions of the device.
This formalism is applied to obtain the spatial distribution of microscopic
spin currents in {\em clean} phase-coherent two-dimensional electron gas with
the Rashba-type of SO coupling attached to four external leads. Together with
the corresponding profiles of the stationary spin density, such visualization
of the phase-coherent spin flow allow us to resolve several key issues for the
understanding of mechanisms which generate pure spin Hall currents in the
transverse leads of ballistic devices due to the flow of unpolarized charge
current through their longitudinal leads. The local spin current profiles
crucially depend on whether the sample is smaller or greater than the spin
precession length, thereby demonstrating its essential role as the
characteristic mesoscale for the spin Hall effect in ballistic multiterminal
semiconductor nanostructures. Although static spin-independent disorder reduces
the magnitude of the total spin current in the leads, the bond spin currents
continue to flow through the whole diffusive 2DEG sample, without being
localized as edge spin currents around any of its boundaries.Comment: 17 pages, 8 color EPS figures; preprint with much higher resolution
figures is available from
http://www.physics.udel.edu/~bnikolic/QTTG/publications.ht
LEVEL CORRELATIONS DRIVEN BY WEAK LOCALIZATION IN 2-D SYSTEMS
We consider the two-level correlation function in two-dimensional disordered
systems. In the non-ergodic diffusive regime, at energy
( is the Thouless energy), it is shown to be completely determined by
the weak localization effects, thus being extremely sensitive to time-reversal
and spin symmetry breaking: it decreases drastically in the presence of
magnetic field or magnetic impurities and changes its sign in the presence of a
spin-orbit interaction. In contrast to this, the variance of the levels number
fluctuations is shown to be almost unaffected by the weak localization effects.Comment: 4 pages, 2 figures, in self-ectracting uuencoded file, submitted to
Phys. Rev. Letters
Composite fermions in the Fractional Quantum Hall Effect: Transport at finite wavevector
We consider the conductivity tensor for composite fermions in a close to
half-filled Landau band in the temperature regime where the scattering off the
potential and the trapped gauge field of random impurities dominates. The
Boltzmann equation approach is employed to calculate the quasiclassical
transport properties at finite effective magnetic field, wavevector and
frequency. We present an exact solution of the kinetic equation for all
parameter regimes. Our results allow a consistent description of recently
observed surface acoustic wave resonances and other findings.Comment: REVTEX, 4 pages, 1 figur
Two-component model of a spin-polarized transport
Effect of the spin-involved interaction of electrons with impurity atoms or
defects to the transport properties of a two-dimensional electron gas is
described by using a simplifying two-component model. Components representing
spin-up and spin-down states are supposed to be coupled at a discrete set of
points within a conduction channel. The used limit of the short-range
interaction allows to solve the relevant scattering problem exactly. By varying
the model parameters different transport regimes of two-terminal devices with
ferromagnetic contacts can be described. In a quasi-ballistic regime the
resulting difference between conductances for the parallel and antiparallel
orientation of the contact magnetization changes its sign as a function of the
length of the conduction channel if appropriate model parameters are chosen.
The effect is in agreement with recent experimental observations.Comment: 4 RevTeX pages with 4 figure
Critical level spacing distribution of two-dimensional disordered systems with spin-orbit coupling
The energy level statistics of 2D electrons with spin-orbit scattering are
considered near the disorder induced metal-insulator transition. Using the Ando
model, the nearest-level-spacing distribution is calculated numerically at the
critical point. It is shown that the critical spacing distribution is size
independent and has a Poisson-like decay at large spacings as distinct from the
Gaussian asymptotic form obtained by the random-matrix theory.Comment: 7 pages REVTeX, 2 uuencoded, gzipped figures; J. Phys. Condensed
Matter, in prin
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