Nonlinear effects in microwave photoconductivity of two-dimensional electron systems

Abstract

We present a model for microwave photoconductivity of two-dimensional\nelectron systems in a magnetic field which describes the effects of strong\nmicrowave and steady-state electric fields. Using this model, we derive an\nanalytical formula for the photoconductivity associated with photon- and\nmulti-photon-assisted impurity scattering as a function of the frequency and\npower of microwave radiation. According to the developed model, the microwave\nconductivity is an oscillatory function of the frequency of microwave radiation\nand the cyclotron frequency which turns zero at the cyclotron resonance and its\nharmonics. It exhibits maxima and minima (with absolute negative conductivity)\nat the microwave frequencies somewhat different from the resonant frequencies.\nThe calculated power dependence of the amplitude of the microwave\nphotoconductivity oscillations exhibits pronounced sublinear behavior similar\nto a logarithmic function. The height of the microwave photoconductivity maxima\nand the depth of its minima are nonmonotonic functions of the electric field.\nIt is pointed to the possibility of a strong widening of the maxima and minima\ndue to a strong sensitivity of their parameters on the electric field and the\npresence of strong long-range electric-field fluctuations. The obtained\ndependences are consistent with the results of the experimental observations.\n