Theory of magnetothermoelectric phenomena in high-mobility two-dimensional electron systems under microwave irradiation

TL;DR

This paper presents a theoretical study of how microwave irradiation affects thermopower in high-mobility two-dimensional electron systems under magnetic fields, revealing oscillations and polarization sensitivity.

Contribution

It introduces a microscopic theory explaining microwave-induced modifications of thermopower, including Landau quantization and interference effects in phonon-drag mechanisms.

Findings

Microwave irradiation causes prominent oscillations in thermopower as a function of magnetic field.

Transverse thermopower is more strongly affected by microwaves than longitudinal thermopower.

Thermopower modifications are highly sensitive to microwave polarization direction.

Abstract

The response of two-dimensional electron gas to temperature gradient in perpendicular magnetic field under steady-state microwave irradiation is studied theoretically. The electric currents induced by temperature gradient and the thermopower coefficients are calculated taking into account both diffusive and phonon-drag mechanisms. The modification of thermopower by microwaves takes place because of Landau quantization of electron energy spectrum and is governed by the microscopic mechanisms which are similar to those responsible for microwave-induced oscillations of electrical resistivity. The magnetic-field dependence of microwave-induced corrections to phonon-drag thermopower is determined by mixing of phonon resonance frequencies with radiation frequency, which leads to interference oscillations. The transverse thermopower is modified by microwave irradiation much stronger than the longitudinal one. Apart from showing prominent microwave-induced oscillations as a function of magnetic field, the transverse thermopower appears to be highly sensitive to the direction of linear polarization of microwave radiation.