Proximitized insulators from disordered superconductors

Abstract

We present an experimental study of bilayers of a disordered Ag metal layer close to the metal-insulator transition and an Indium Oxide film which is on the insulating side of the superconductor-insulator-transition. Our results show that superconducting fluctuations within the indium-oxide film, that proximitize the underlying metal layer, induce insulating rather than superconducting behavior. This is ascribed to suppression of density of states (due to the superconducting energy gap) for quasiparticles in the proximitized regions. Our results present a novel manifestation of the proximity effect phenomenon and provide important insight into the nature of the insulating phase of the disorder driven superconductor-insulator-transition.