Melting of Wigner crystal in high-mobility $n$-GaAs/AlGaAs heterostructures at filling factors $0.18 > \nu > 0.125$: Acoustic studies

TL;DR

This study uses acoustic techniques to investigate the melting of a Wigner crystal in high-mobility GaAs/AlGaAs heterostructures at low temperatures and high magnetic fields, revealing how disorder and filling factor influence phase transitions.

Contribution

It provides the first acoustic evidence of Wigner crystal melting in GaAs/AlGaAs heterostructures and explores the dependence on filling factor and temperature.

Findings

Wigner crystal forms at low temperatures and high magnetic fields.

Melting temperature varies with electron filling factor.

Acoustic conductance reveals phase transition details.

Abstract

Using acoustic methods the complex high-frequency conductance of high-mobility $n$-GaAs/AlGaAs heterostructures was determined in magnetic fields 12$\div$18~T. Based on the observed frequency and temperature dependences we conclude that in the investigated magnetic field range and at sufficiently low temperatures, $T \lesssim 200$~mK, the electron system forms a Wigner crystal deformed due to pinning by disorder. At some temperature, which depends on the electron filling factor, the temperature dependences of both components of the complex conductance get substantially changed. We have ascribed this rapid change of the conduction mechanism to melting of the Wigner crystal and study the dependence of the so-defined melting temperature on the electron filling factor.