Theory of microwave-induced oscillations in the magnetoconductivity of a two-dimensional electron gas

Abstract

We develop a theory of magnetooscillations in the photoconductivity of a two-dimensional electron gas observed in recent experiments. The effect is governed by a change of the electron distribution function induced by the microwave radiation. We analyze a nonlinearity with respect to both the dc field and the microwave power, as well as the temperature dependence determined by the inelastic relaxation rate.

Zero-Differential Resistance State of Two-Dimensional Electron Systems in Strong Magnetic Fields

“…In the paper [16] the strong reduction of the resistance has been attributed to substantial changes of the electron distribution function induced by the DC electric field E dc . Reasonable agreement has been established between the experiment and recent theory [12].…”

“…higher temperatures the differential resistance, although becoming quite small, does not demonstrate the transition to the zero differential resistance state. A possible reason of such behavior is that at higher temperatures the nonlinear response to the dc bias is much weaker, due to substantial increase of the electron-electron scattering at high temperature [12,16]. The weaker nonlinearity requires stronger dc biases for the same nonlinear change of the resistance.…”

“…The high density of states enhances significantly the electron diffusion in the energy space providing strong nonlinear response to the dc bias [12,16]. Fig.2b demonstrates the dependence of the r xx on the dc bias taken at different magnetic fields corresponding to SdH maximums.…”

“…One is related to the decrease of the modulation of the density of states with the energy at low magnetic fields due to substantial overlap of Landau levels. The weak modulation of the density of states makes the diffusion in the energy space to be more uniformed and, in result, the magnitude of the oscillating non-equilibrium distribution function and the nonlinear conductivity become to be small [12,16]. Another reason is the increase of the (bias induced) inter Landau level scattering due to the decrease of the Landau level separation at low magnetic field [14,18].…”

“…[3,4,5,6] This so-called zero resistance state (ZRS) has stimulated extensive theoretical interest. [7,8,9,10,11,12] At higher magnetic field ω c > ω a considerable decrease of magnetoresistance with microwave power is found [2,5,6] which has been attributed to intra-Landau-level transitions. [13] Another interesting nonlinear phenomena have been observed in response to DC electric field.…”