728 research outputs found
Disorder effect of resonant spin Hall effect in a tilted magnetic field
We study the disorder effect of resonant spin Hall effect in a two-dimension
electron system with Rashba coupling in the presence of a tilted magnetic
field. The competition between the Rashba coupling and the Zeeman coupling
leads to the energy crossing of the Landau levels, which gives rise to the
resonant spin Hall effect. Utilizing the Streda's formula within the
self-consistent Born approximation, we find that the impurity scattering
broadens the energy levels, and the resonant spin Hall conductance exhibits a
double peak around the resonant point, which is recovered in an applied titled
magnetic field.Comment: 6 pages, 4 figure
Theory of resonant spin Hall effect
A biref review is presented on resonant spin Hall effect, where a tiny
external electric field induces a saturated spin Hall current in a
2-dimensional electron or hole gas in a perpendicular magnetic field. The
phenomenon is attributted to the energy level crossing associated with the
spin-orbit coupling and the Zeeman splitting. We summarize recent theoretical
development of the effect in various systems and discuss possible experiments
to observe the effect.Comment: 5 pages with 1 figure
Theory of magnetoelectric photocurrent generated by direct interband transitions in semiconductor quantum well
A linearly polarized light normally incident on a semiconductor quantum well
with spin-orbit coupling may generate pure spin current via direct interband
optical transition. An electric photocurrent can be extracted from the pure
spin current when an in-plane magnetic field is applied, which has been
recently observed in the InGaAs/InAlAs quantum well [Dai et al., Phys. Rev.
Lett. 104, 246601 (2010)]. Here we present a theoretical study of this
magnetoelectric photocurrent effect associated with the interband transition.
By employing the density matrix formalism, we show that the photoexcited
carrier density has an anisotropic distribution in k space, strongly dependent
on the orientation of the electron wavevector and the polarization of the
light. This anisotropy provides an intuitive picture of the observed dependence
of the photocurrent on the magnetic field and the polarization of the light. We
also show that the ratio of the pure spin photocurrent to the magnetoelectric
photocurrent is approximately equal to the ratio of the kinetic energy to the
Zeeman energy, which enables us to estimate the magnitude of the pure spin
photocurrent. The photocurrent density calculated with the help of an
anisotropic Rashba model and the Kohn-Luttinger model can produce all three
terms in the fitting formula for measured current, with comparable order of
magnitude, but discrepancies are still present and further investigation is
needed.Comment: 13 pages, 9 figures, 2 table
Transverse electric current induced by optically injected spin current in cross-shaped InGaAs/InAlAs system
We examine electric response of a linearly polarized light normally shed on a
cross-shaped quasi 2-dimensional InGaAs/InAlAs system with structure inversion
asymmetry. The photo-excited conduction electrons carry a pure spin current
with in-plane spin polarization due to the Rashba spin-orbit interaction. We
use Landauer-B\"{u}ttiker formalism to show that this spin current induces two
inward or outward transverse charge currents, which are observable in
experiments. This effect may serve as an experimental probe of certain types of
spin current.Comment: 5 pages, 3 figure
Localization and Mobility Gap in Topological Anderson Insulator
It has been proposed that disorder may lead to a new type of topological
insulator, called topological Anderson insulator (TAI). Here we examine the
physical origin of this phenomenon. We calculate the topological invariants and
density of states of disordered model in a super-cell of 2-dimensional
HgTe/CdTe quantum well. The topologically non-trivial phase is triggered by a
band touching as the disorder strength increases. The TAI is protected by a
mobility gap, in contrast to the band gap in conventional quantum spin Hall
systems. The mobility gap in the TAI consists of a cluster of non-trivial
subgaps separated by almost flat and localized bands.Comment: 8 pages, 7 figure
Observation of electric current induced by optically injected spin current
A normally incident light of linear polarization injects a pure spin current
in a strip of 2-dimensional electron gas with spin-orbit coupling. We report
observation of an electric current with a butterfly-like pattern induced by
such a light shed on the vicinity of a crossbar shaped InGaAs/InAlAs quantum
well. Its light polarization dependence is the same as that of the spin
current. We attribute the observed electric current to be converted from the
optically injected spin current caused by scatterings near the crossing. Our
observation provides a realistic technique to detect spin currents, and opens a
new route to study the spin-related science and engineering in semiconductors.Comment: 15 pages, 4 figure
Resonant Spin Hall Conductance in Two-Dimensional Electron Systems with Rashba Interaction in a Perpendicular Magnetic Field
We study transport properties of a two-dimensional electron system with
Rashba spin-orbit coupling in a perpendicular magnetic field. The spin orbit
coupling competes with Zeeman splitting to introduce additional degeneracies
between different Landau levels at certain magnetic fields. This degeneracy, if
occuring at the Fermi level, gives rise to a resonant spin Hall conductance,
whose height is divergent as 1/T and whose weight is divergent as at
low temperatures. The Hall conductance is unaffected by the Rashba coupling.Comment: 4 pages, 4 figure
Tunable Goos-H\"{a}nchen shift and polarization beam splitter in electro-optic crystals
We have investigated the tunable lateral shift and polarization beam
splitting of the transmitted light beam through electro-optic crystals, based
on the Pockels effect. The positive and negative lateral shifts could be easily
controlled by adjusting the permittivity tensor, which is modulated by the
external applied electric field. An alternative way to realize the polarization
beam splitter was also proposed by the polarization-dependent lateral shifts.
Numerical simulations for Gaussian-shaped incident beam have demonstrated the
above theoretical results obtained by stationary phase method. All these
phenomena have potential applications in optical devices.Comment: 5 pages, 7 figure
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