Low-Frequency Microwave Induced Quantum Oscillations in A Two-Dimensional Electron System

TL;DR

This study investigates how low-frequency microwave irradiation affects magnetoresistance oscillations in high-mobility two-dimensional electron systems, revealing a transition from MIRO to a new oscillation possibly linked to ac-HIRO or multi-photon processes.

Contribution

It demonstrates the emergence of a new SdH-like oscillation at very low microwave frequencies and connects MIRO and HIRO phenomena within a quantum tunneling framework.

Findings

MIRO dampens with decreasing microwave frequency

A new SdH-like oscillation appears at f < 4 GHz

The new oscillation may originate from ac-HIRO or multi-photon MIRO processes

Abstract

We study the magnetoresistance of an ultrahigh mobility GaAs/AlGaAs two-dimensional electron sample in a weak magnetic field under low-frequency (f < 20 GHz) microwave (MW) irradiation. We observe that with decreasing MW frequency, microwave induced resistance oscillations (MIRO) damp and multi-photon processes become dominant. At very low MW frequency (f < 4 GHz), MIRO disappears gradually and a new SdH-like oscillation develops. The analysis indicates that the new oscillation may originate from alternating Hall-field induced resistance oscillations (ac-HIRO), or can be viewed as a multi-photon process of MIRO in low MW frequency limit. Our findings bridge the non-equilibrium states of MIRO and HIRO, which can be brought into a frame of quantum tunneling junction model.