Speaker: Ivan Dmitriev, Institute for Theoretical Physics, Karlsruhe University, Germany
Abstract: We propose a unified quantum kinetic description of a family of nonequilibrium magnetooscillations recently discovered in high-mobility quantum Hall structures, including the microwave induced resistance oscillations (MIRO), Hall-field induced RO (HIRO), and phonon induced RO (PIRO). The magnetoresistivity is due to quantum oscillations in the density of states in high Landau levels and is governed by spectral and spatial resonances set by the cyclotron frequency and the cyclotron diameter in various combinations with the parameters of the external fields and phonons. External ac or dc driving leads to local population inversion in the energy distribution of electrons and modifies the scattering off impurities and phonons. In particular, PIRO are shown to be very sensitive to the applied direct current. In the supersonic regime, where the Hall velocity exceeds the sound velocity, the phonon-assisted conductivity remains finite at zero temperature, while below the supersonic transition the oscillations get exponentially suppressed at low temperature. Quite interestingly, in the microwave-illuminated inhomogeneous 2D electron gas, the photocurrent and photovoltage oscillations arise in the absence of the external dc driving, due to nonequilibrium violation of the Einstein relation between electrical current and diffusion.