Metal-insulator transition at B=0 in a dilute two dimensional GaAs-AlGaAs hole gas

TL;DR

This paper reports the observation of a metal-insulator transition at zero magnetic field in a high mobility two-dimensional hole gas, highlighting a critical point with a minimum metallic conductivity and the effects of magnetic fields on the transition.

Contribution

It provides experimental evidence of a well-defined metal-insulator transition at B=0 in a 2D hole gas, emphasizing the role of electron-electron interactions in destroying phase coherence.

Findings

Existence of a critical point separating metallic and insulating phases.

Identification of a minimum metallic conductivity sigma(min)=2e/h.

Magnetic field effects include increased sigma(min) and transition broadening.

Abstract

We report the observation of a metal insulator transition at B=0 in a high mobility two dimensional hole gas in a GaAs-AlGaAs heterostructure. A clear critical point separates the insulating phase from the metallic phase, demonstrating the existence of a well defined minimum metallic conductivity sigma(min)=2e/h. The sigma(T) data either side of the transition can be `scaled' on to one curve with a single parameter (To). The application of a parallel magnetic field increases sigma(min) and broadens the transition. We argue that strong electron-electron interactions (rs = 10) destroy phase coherence, removing quantum intereference corrections to the conductivity.