Microwave photoresistance in a two-dimensional electron gas with separated Landau levels

TL;DR

This study investigates microwave photoresistance in a 2D electron gas, revealing that maxima positions do not shift with increasing frequency as predicted, challenging existing theories about Landau level separation effects.

Contribution

The paper provides experimental evidence that contradicts current models linking photoresistance maxima to Landau level separation at higher frequencies.

Findings

Maxima move towards harmonics with decreasing oscillation order n

No movement of maxima with increasing frequency ω for fixed n

Challenges current understanding of microwave-induced resistance oscillations

Abstract

Theories of microwave-induced resistance oscillations in high-mobility two-dimensional electron gas predict that with decreasing oscillation order $n$ or with increasing frequency $\omega$ the photoresistance maxima should appear closer to the cyclotron resonance harmonics due to increased Landau level separation. In this experimental study we demonstrate that while for a given $\omega$ the peaks do move towards the harmonics with decreasing $n$, there is no corresponding movement with increasing $\omega$ for a given $n$. These findings show that the positions of the photoresistance maxima cannot be directly linked to the Landau level separation challenging our current understanding of the phenomenon.