Electron localization in sound absorption oscillations in the quantum Hall effect regime

TL;DR

This study investigates how surface acoustic wave absorption varies with magnetic field, frequency, and temperature in a GaAs/AlGaAs heterostructure, revealing electron localization effects in the quantum Hall regime.

Contribution

It provides experimental analysis of acoustic wave absorption linked to electron localization in the quantum Hall effect, incorporating frequency, magnetic field, and temperature dependencies.

Findings

Absorption coefficient varies with magnetic field, frequency, and temperature.

Electron localization occurs in energy tails of Landau levels.

Results support the existence of a fluctuation potential causing localization.

Abstract

The absorption coefficient for surface acoustic waves in a piezoelectric insulator in contact with a GaAs/AlGaAs heterostructure (with two-dimensional electron mobility $\mu= 1.3\times 10^5 cm^2/V\cdot s)$ at T=4.2K) via a small gap has been investigated experimentally as a function of the frequency of the wave, the width of the vacuum gap, the magnetic field, and the temperature. The magnetic field and frequency dependencies of the high-frequency conductivity (in the region 30-210 MHz) are calculated and analyzed. The experimental results can be explained if it assumed that there exists a fluctuation potential in which current carrier localization occurs. The absorption of the surface acoustic waves in an interaction with two-dimensional electrons localized in the energy "tails" of Landau levels is discussed.