14,675 research outputs found
Radiation-induced magnetoresistance oscillation in a two-dimensional electron gas in Faraday geometry
Microwave-radiation induced giant magnetoresistance oscillations recently
discovered in high-mobility two-dimensional electron systems in a magnetic
field, are analyzed theoretically. Multiphoton-assisted impurity scatterings
are shown to be the primary origin of the oscillation. Based on a model which
considers the interaction of electrons with the electromagnetic fields in
Faraday geometry, we are able not only to reproduce the correct period, phase
and the negative resistivity of the main oscillation, but also to obtain
secondary peaks and additional maxima and minima in the resistivity curve, some
of which were already observed in the experiments.Comment: 4 pages, 1 figure, revised version to be published in Phys. Rev. Let
Disorder effects on the spin-Hall current in a diffusive Rashba two-dimensional heavy-hole system
We investigate the spin-Hall effect in a two-dimensional heavy-hole system
with Rashba spin-orbit coupling using a nonequilibrium Green's function
approach. Both the short- and long-range disorder scatterings are considered in
the self-consistent Born approximation. We find that, in the case of long-range
collisions, the disorder-mediated process leads to an enhancement of the
spin-Hall current at high heavy-hole density, whereas for short-range
scatterings it gives a vanishing contribution. This result suggests that the
recently observed spin-Hall effect in experiment is a result of the sum of the
intrinsic and disorder-mediated contributions. We have also calculated the
temperature dependence of spin-Hall conductivity, which reveals a decrease with
increasing the temperature.Comment: 5 pages, 2 figures, Typos in the values of hole density correcte
Direct-current control of radiation-induced differential magnetoresistance oscillations in two-dimensional electron systems
Magnetoresistance oscillations in two-dimensional electron systems driven
simultaneously by a strong direct current and a microwave irradiation, are
analyzed within a unified microscopic scheme treating both excitations on an
equal footing. The microwave-induced resistance oscillations are described by a
parameter proportional to the radiation frequency, while the
dc-induced resistance oscillations are governed by a parameter
proportional to the current density. In the presence of both a microwave
radiation and a strong dc, the combined parameter
is shown to control the main resistance oscillations, in agreement with the
recent measurement [Zhang {\it et al.} Phys. Rev. Lett. {\bf 98}, 106804
(2007)]Comment: 4 pages, 2 figues, published versio
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