Evidence for current flow anomalies in the irradiated 2D electron system at small magnetic fields

TL;DR

This study investigates low-temperature magnetotransport in high mobility 2D electron systems under microwave radiation, revealing anomalies in magnetoresistance oscillations and current instabilities not fully explained by existing theories.

Contribution

It provides new experimental evidence of current flow anomalies and radiation-induced transport phenomena at low magnetic fields in irradiated 2D electron systems.

Findings

Magnetoresistance oscillations extend to negative biases.

Voltage signals observed without applied currents.

Minima are highly power-dependent and not fully understood.

Abstract

We report experimental results of low temperature magnetotransport in high mobility 2D electron systems exposed to radiation up to 20GHz frequency using a simple dipole configuration. Magnetoresistance oscillations are observed as in previously reported higher frequency radiation on 2D systems, however minima here can be seen to extend to negative biases, and zeroes previously reported are not observed persistently around the full sample perimeters. In addition, under radiation, voltages are observed from internal to external contacts in the absence of applied driving currents not due to simple rectification. These findings are consistent with micro- and macroscopic theoretical pictures of radiation induced transport and current instabilities due to local negative resistivities. However, the temperature dependent development of minima is shown to be severely power dependent, and outside of present theoretical understanding.