Terahertz dynamics of a topologically protected state: quantum Hall effect plateaus near cyclotron resonance in a GaAs/AlGaAs heterojunction

TL;DR

This study investigates the terahertz frequency behavior of quantum Hall effect plateaus in a GaAs/AlGaAs heterojunction, revealing topologically protected edge states through Faraday rotation measurements near cyclotron resonance.

Contribution

It demonstrates the observation of quantum Hall plateaus at terahertz frequencies using a novel Faraday rotation technique combined with electrical gating.

Findings

Clear plateau-and step-like features in Faraday rotation angle observed.

Quantum Hall plateaus manifest at high frequencies near cyclotron resonance.

Results align with recent dynamical scaling theory.

Abstract

We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency by employing a highly sensitive Faraday rotation method coupled with electrical gating of the sample to change the electron density. We observe clear plateau-and step-like features in the Faraday rotation angle vs. electron density and magnetic field (Landau-level filling factor), which are the high frequency manifestation of quantum Hall plateaus - a signature of topologically protected edge states. The results are compared to a recent dynamical scaling theory.