Bichromatic Microwave Photoresistance of Two-Dimensional Electron System

TL;DR

This study investigates how bichromatic microwave frequencies affect photoresistance in a two-dimensional electron system, revealing superposition behavior under certain conditions and suppression when zero-resistance states occur.

Contribution

It provides experimental evidence on the superposition principle for bichromatic photoresistance and identifies conditions where this principle breaks down in zero-resistance states.

Findings

Bichromatic resistance is additive when both monochromatic resistances are positive.

Superposition relation breaks down in the presence of zero-resistance states.

Bichromatic resistance is suppressed when a zero-resistance state is formed by one frequency.

Abstract

We explore experimentally bichromatic (frequencies $\omega_1$ and $\omega _2$) photoresistance of a two-dimensional electron system in the regimes of microwave-induced resistance oscillations and zero-resistance states. We find bichromatic resistance to be well described by a superposition of $\omega_1$ and $\omega_2$ components, provided that both monochromatic resistances are positive. This relation holds even when the oscillation amplitudes are small and one could expect additive contributions from monochromatic photoresistances. In contrast, whenever a zero-resistance state is formed by one of the frequencies, such superposition relation breaks down and the bichromatic resistance is strongly suppressed.