Photoemission study of the transition from the insulating to metallic state in ultrathin layers

Abstract

The transition from the insulating to metallic state in ultrathin Pb films was studied using high-resolution photoemission. The states near ${\mathrm{E}}_{\mathrm{F}}$ were probed as Pb was deposited onto a thin insulating layer, thin enough to reduce macroscopic charging. The results, which experimentally show a vanishing of states at ${\mathrm{E}}_{\mathrm{F}}$, are consistent with the arguments of Efros and Shklovskii based on electron-electron interactions, and as far as we know are the first in situ study of the electronic properties as one goes from the insulating to metallic state in a two-dimensional system.