The superconductor insulator transition in systems of ultrasmall grains

Abstract

We present transport measurements on quench condensed granular Pb films in which the grains are 40-80Åin diameter. These films show a cross over from an insulator to a superconductor behavior as the nominal thickness of the layer is increased. This transition is different in nature than those seen in quench condensed systems reported in the past where the films were either uniform or granular with grain sizes on the order of 200Å. We discuss possible physical mechanisms for these transitions.