Fractional microwave-induced resistance oscillations

TL;DR

This paper presents a comprehensive theory explaining microwave-induced resistance oscillations near fractional harmonics in a 2D electron gas, highlighting the dominant multiphoton inelastic mechanism at high magnetic fields and two single-photon mechanisms at moderate fields.

Contribution

It introduces a systematic theoretical framework for fractional microwave-induced resistance oscillations, emphasizing the roles of multiphoton and single-photon mechanisms across different magnetic field regimes.

Findings

Dominance of multiphoton inelastic mechanism near well-separated Landau levels.

Identification of two single-photon mechanisms at moderate magnetic fields.

Explanation of experimental observations of fractional oscillations.

Abstract

We develop a systematic theory of microwave-induced oscillations in magnetoresistivity of a 2D electron gas in the vicinity of fractional harmonics of the cyclotron resonance, observed in recent experiments. We show that in the limit of well-separated Landau levels the effect is dominated by the multiphoton inelastic mechanism. At moderate magnetic field, two single-photon mechanisms become important. One of them is due to resonant series of multiple single-photon transitions, while the other originates from microwave-induced sidebands in the density of states of disorder-broadened Landau levels.