Microwave photoconductivity of a 2D electron gas: Mechanisms and their interplay at high radiation power

摘要

We develop a systematic theory of microwave-induced oscillations in themagnetoresistivity of a two-dimensional electron gas, focusing on the regime ofstrongly overlapping Landau levels. At linear order in microwave power, twonovel mechanisms of the oscillations (``quadrupole'' and ``photovoltaic'') areidentified, in addition to those studied before (``displacement'' and``inelastic''). The quadrupole and photovoltaic mechanisms are shown to be theonly ones that give rise to oscillations in the nondiagonal part of thephotoconductivity tensor. In the diagonal part, the inelastic contributiondominates at moderate microwave power, while at elevated power the othermechanisms become relevant. We demonstrate the crucial role of feedbackeffects, which lead to a strong interplay of the four mechanisms in thenonlinear photoresponse and yield, in particular, a nonmonotonic powerdependence of the photoconductivity, narrowing of the magnetoresonances, and anontrivial structure of the Hall photoresponse. At ultrahigh power, all effectsrelated to the Landau quantization decay due to a combination of the feedbackand multiphoton effects, restoring the classical Drude conductivity.