1,553 research outputs found
Effect of boundary scattering on spin-hall effect
The spin dependent reflection in quasi-two-dimensional electron gas from an
impenetrable barrier in presence of Rashba and Dresselhaus spin-orbit coupling
is analyzed in detail. It is shown that due to spin-orbit effects the reflected
beam split in two beams gives rise to multiple reflection analogous to
phenomena birefringence. The interplay between Rashba and Dresselhaus
spin-orbit coupling gives rise to anisotropy in Fermi energy surface and a
non-zero net spin-polarized current oscillating with two frequencies for all
the values of incident angle except at when averaged over all
components of reflected beam. It is also shown that in over critical region,
all the three polarization components as well as net polarization has non-zero
values and are exponentially decaying as distance from the barrier increases
which in turns spin-accumulation near the barrier is an important consequence
of spin-hall effect.Comment: 6 pages, 8 figure
Ground state properties of dissipative two state system coupled to phonons
We present a systematic analysis of ground state properties of a tunneling
system coupled to an Ohmic bath. The nonadiabatic effects induced by coupling
with tunneling particle , on the ground state properties of phonons are taken
into account. For this we have considered both displacement and deformation of
phonons via a variational treatment. The symmetry breaking transition , or the
delocalization-localization transition of tunneling particle is presented and
is compared with earlier known results. We also show that in the critical
regime a gap will be opened near the zero momentum in the spectrum of the
phonons. The modified phonon spectrum along with the phonon displacement field
correlation functions have been calculated. It is shown that in the critical
regime the tunneling system stabilizes the lattice against long wavelength
fluctuations.Comment: To appear in IJOMPB. 5 figures available on reques
Stochastic resonance and nonlinear response in a dissipative quantum two-state system
We study the dynamics of a dissipative two-level, system driven by a
monochromatic ac field, starting from the usual spin-boson Hamiltonian. The
quantum Langevin equations for the spin variables are obtained. The amplitude
of the coherent oscillations in the average position of the particle is studied
in the high temperature limit. The system exhibits quantum stochastic resonance
in qualitative agreement with earlier numerical results.Comment: PRB April 1997, figures available on reques
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