Metallic behaviour and localisation in 2D GaAs hole systems

We have investigated the apparent "metal"-insulator transition in a variety of high quality 2D GaAs hole systems. Central to the issue of whether such a transition can exist is the question of what happens to the localising q uantum corrections to the conductivity predicted by one-parameter scaling t heory. We demonstrate that in samples where the phase coherence length is g reater than the mean free path, weak localisation corrections are observed in the so-called "metallic" phase, We also observe weak hole-hole interacti on corrections close to but on the "metallic" side of the transition. Both these corrections are localising, becoming stronger as T -->0. This suggest s that despite the strong interactions (r(s) > 10) these 2D GaAs hole syste ms still behave like Fermi liquids, and there is no true 2D "metallic" stat e. Instead, we find that conventional temperature dependent screening can a ccount for many aspects of the metallic behaviour. (C) 2001 Elsevier Scienc e BN. All rights reserved.