Nonlinear effects in microwave photoconductivity of two-dimensional electron systems

TL;DR

This paper develops a theoretical model for microwave photoconductivity in two-dimensional electron systems under strong fields, predicting oscillatory behavior and nonlinear power dependence consistent with experimental data.

Contribution

The paper introduces an analytical model capturing nonlinear microwave photoconductivity effects, including multi-photon processes and electric field influences, in 2D electron systems under magnetic fields.

Findings

Microwave photoconductivity oscillates with frequency and cyclotron frequency.

Maxima and minima in conductivity are sensitive to electric field strength.

Power dependence of oscillation amplitude is sublinear, resembling a logarithmic trend.

Abstract

We present a model for microwave photoconductivity of two-dimensional electron systems in a magnetic field which describes the effects of strong microwave and steady-state electric fields. Using this model, we derive an analytical formula for the photoconductivity associated with photon- and multi-photon-assisted impurity scattering as a function of the frequency and power of microwave radiation. According to the developed model, the microwave conductivity is an oscillatory function of the frequency of microwave radiation and the cyclotron frequency which turns zero at the cyclotron resonance and its harmonics. It exhibits maxima and minima (with absolute negative conductivity) at the microwave frequencies somewhat different from the resonant frequencies. The calculated power dependence of the amplitude of the microwave photoconductivity oscillations exhibits pronounced sublinear behavior similar to a logarithmic function. The height of the microwave photoconductivity maxima and the depth of its minima are nonmonotonic functions of the electric field. It is pointed to the possibility of a strong widening of the maxima and minima due to a strong sensitivity of their parameters on the electric field and the presence of strong long-range electric-field fluctuations. The obtained dependences are consistent with the results of the experimental observations.