Disappearance of the metal-like behavior in GaAs two-dimensional holes below 30 mK

TL;DR

This study investigates the temperature-dependent resistivity of two-dimensional holes in GaAs, revealing a transition from metal-like to insulator-like behavior below 30 mK, challenging previous expectations of metallic behavior at low temperatures.

Contribution

It provides experimental evidence of the disappearance of metallic behavior in GaAs 2D holes below 30 mK, highlighting a crossover to insulating behavior.

Findings

Resistivity changes sign around 30 mK

Resistivity increases continuously below 30 mK

Metal-insulator transition behavior observed at higher temperatures

Abstract

The zero-field temperature-dependence of the resistivity of two-dimensional holes are observed to exhibit two qualitatively different characteristics for a fixed carrier density for which only the metallic behavior of the so-called metal-insulator transition is anticipated. As $T$ is lowered from 150 mK to 0.5 mK, the sign of the derivative of the resistivity with respect to $T$ changes from being positive to negative when the temperature is lowered below $\sim$30 mK and the resistivity continuously rises with cooling down to 0.5 mK, suggesting a crossover from being metal-like to insulator-like.