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

TL;DR

This paper develops a comprehensive theory of microwave-induced oscillations in the magnetoresistivity of a 2D electron gas, revealing new mechanisms and their complex interplay at high radiation power, with implications for understanding nonlinear photoresponses.

Contribution

It introduces two novel mechanisms, quadrupole and photovoltaic, and explores their interplay with known effects in high-power regimes, advancing the theoretical understanding of microwave photoconductivity.

Findings

Identification of quadrupole and photovoltaic mechanisms.

Nonmonotonic power dependence of photoconductivity.

Restoration of classical conductivity at ultrahigh power.

Abstract

We develop a systematic theory of microwave-induced oscillations in the magnetoresistivity of a two-dimensional electron gas, focusing on the regime of strongly overlapping Landau levels. At linear order in microwave power, two novel mechanisms of the oscillations (``quadrupole'' and ``photovoltaic'') are identified, in addition to those studied before (``displacement'' and ``inelastic''). The quadrupole and photovoltaic mechanisms are shown to be the only ones that give rise to oscillations in the nondiagonal part of the photoconductivity tensor. In the diagonal part, the inelastic contribution dominates at moderate microwave power, while at elevated power the other mechanisms become relevant. We demonstrate the crucial role of feedback effects, which lead to a strong interplay of the four mechanisms in the nonlinear photoresponse and yield, in particular, a nonmonotonic power dependence of the photoconductivity, narrowing of the magnetoresonances, and a nontrivial structure of the Hall photoresponse. At ultrahigh power, all effects related to the Landau quantization decay due to a combination of the feedback and multiphoton effects, restoring the classical Drude conductivity.