Metal-Insulator Transition at B = 0 in a Dilute Two Dimensional GaAs-AlGaAs Hole Gas

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 σ_min = 2e²/h. The σ(T) data either side of the transition can be “scaled” onto one curve with a single parameter T₀. The application of a parallel magnetic field increases σ_min and broadens the transition. We argue that strong electron-electron interactions ( r_s≃10) suppress quantum interference corrections to the conductivity.