Circular polarization immunity of the cyclotron resonance photoconductivity in two-dimensional electron systems

TL;DR

This paper investigates unexpected cyclotron resonance photoconductivity in 2D electron systems, revealing a polarization immunity that challenges conventional theories and suggesting a modified electron interaction mechanism near impurities.

Contribution

It demonstrates anomalous CR photoconductivity in both geometries, contradicting traditional models, and proposes a new explanation involving local near-field coupling near impurities.

Findings

CR photoconductivity observed in CR-inactive geometry

Contradicts conventional CR theory predictions

Proposes modified electron dynamics near impurities

Abstract

Studying the cyclotron resonance (CR)-induced photoconductivity in GaAs and HgTe two-dimensional electron structures, we observed an anomalous photoresponse for the CR-inactive geometry being of almost the same magnitude as the CR-active one. This observation conflicts with simultaneous transmission measurements and contradicts the conventional theory of CR which predicts no resonant response for the CR-inactive geometry. We provide a possible route to explain this fundamental failure of the conventional description of light-matter interaction and discuss a modified electron dynamics near strong impurities that may provide a local near-field coupling of the two helicity modes of the terahertz field at low temperatures. This should result in a CR-enhanced local absorption and, thus, CR photoconductivity for both magnetic field polarities.