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 sigma(min) = 2e(2)/h. The sigma(T) data either side of the transition can be "scaled" onto one curve with a single parameter T-0. The application of a parallel magnetic field increases sigma(min) and broadens the transition. We argue that strong electron-electron interactions (r(s) similar or equal to 10) suppress quantum interference corrections to the conductivity.