Radiation-induced Magnetoresistance Oscillations Research Articles

Theoretical analysis of radiation-induced magnetoresistance oscillations in high-mobilitytwo-dimensional electron systems

We present a detailed theoretical investigation of the radiation induced giantmagnetoresistance oscillations recently discovered in high-mobility two-dimensional electrongas. Electron interactions with impurities, and transverse and longitudinal acousticphonons in GaAs-based heterosystems are considered simultaneously. Multiphoton-assistedimpurity scatterings are shown to be the primary origin of the resistance oscillation.Based on the balance-equation theory developed for magnetotransport in Faradaygeometry, we are able not only to reproduce the observed period, phase and thenegative resistivity of the main oscillations, but also to predict the secondarypeak/valley structures relating to two-photon and three-photon processes. Thedependence of the magnetoresistance oscillation on microwave intensity, the role ofdc bias current and the effect of elevated electron temperature are discussed.Furthermore, we propose that the temperature dependence of the resistance oscillationstems from the growth of the Landau level broadening due to the enhancement ofacoustic phonon scattering with increasing lattice temperature. The calculatedtemperature variation of the oscillation agrees well with experimental observations.

Radiation-induced oscillatory magnetoresistance as a sensitive probe of the zero-field spin-splitting in high-mobilityGaAs/AlxGa1−xAsdevices

We suggest an approach for characterizing the zero-field spin splitting of high mobility two-dimensional electron systems, when beats are not readily observable in the Shubnikov-de Haas effect. The zero-field spin splitting and the effective magnetic field seen in the reference frame of the electron is evaluated from a quantitative study of beats observed in radiation-induced magnetoresistance oscillations.

Radiation-induced magnetoresistance oscillations in a 2D electron gas

Remarkable recent experiments have shown that microwave radiation can induce dramatic changes in the DC transport properties of a high mobility two-dimensional electron gas. In particular, the diagonal resistivity is an oscillatory function of ω/ ω c, where ω is the microwave frequency and ω c is the cyclotron frequency. The amplitude of the oscillations increases with microwave intensity and eventually saturates as the minimum resistivity approaches zero. We describe a simple model, first proposed many years ago by Ryzhii and collaborators, to explain the effect, and present simplified but detailed and non-perturbative calculations of the non-equilibrium response of the electron gas. We also review some of the many different theoretical pictures that have been proposed to explain the physics and discuss open questions which remain.

Radiation-induced magnetoresistance oscillations in a 2D electron gas.

Recent measurements of a 2D electron gas subjected to microwave radiation reveal a magnetoresistance with an oscillatory dependence on the ratio of radiation frequency to cyclotron frequency. We perform a diagrammatic calculation and find radiation-induced resistivity oscillations with the correct period and phase. Results are explained via a simple picture of current induced by photoexcited disorder-scattered electrons. The oscillations increase with radiation intensity, easily exceeding the dark resistivity and resulting in negative-resistivity minima. At high intensity, we identify additional features, likely due to multiphoton processes, which have yet to be observed experimentally.