14,413 research outputs found

    Radiation-induced magnetoresistance oscillation in a two-dimensional electron gas in Faraday geometry

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    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

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    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

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    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 ϵω\epsilon_\omega proportional to the radiation frequency, while the dc-induced resistance oscillations are governed by a parameter ϵj\epsilon_j proportional to the current density. In the presence of both a microwave radiation and a strong dc, the combined parameter ϵω+ϵj\epsilon_\omega+\epsilon_j 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