Circular-Polarization-Dependent Study of Microwave-Induced Conductivity Oscillations in a Two-Dimensional Electron Gas on Liquid Helium

TL;DR

This study investigates how the polarization of microwaves affects conductivity oscillations in a 2D electron system on liquid helium, revealing a strong polarization dependence that supports photon-assisted scattering models.

Contribution

It provides experimental evidence of polarization dependence in microwave-induced conductivity oscillations on liquid helium, clarifying the mechanism behind these phenomena.

Findings

Strong dependence of oscillation amplitude on circular polarization direction

Supports photon-assisted scattering as the mechanism

Contrasts with semiconductor 2D electron systems

Abstract

The polarization dependence of photoconductivity response at cyclotron-resonance harmonics in a nondegenerate two-dimensional (2D) electron system formed on the surface of liquid helium is studied using a setup in which a circular polarization of opposite directions can be produced. Contrary to the results of similar investigations reported for semiconductor 2D electron systems, for electrons on liquid helium, a strong dependence of the amplitude of magnetoconductivity oscillations on the direction of circular polarization is observed. This observation is in accordance with theoretical models based on photon-assisted scattering and, therefore, it solves a critical issue in the dispute over the origin of microwave-induced conductivity oscillations.