Pressure Induced Anomalous Metal in the Vicinity of the Superconductor Insulator Transition

Abstract

The Superconductor-to-Insulator Transition (SIT) in two-dimensional superconductors occurs due to a competition between superconductivity, quantum interferences, Coulomb interactions and disorder. Despite extensive theoretical and experimental investigation, the SIT remains an active research area due to the potential for exotic phases near the transition. One such phase is the Anomalous Metal, which has been claimed to exist between the insulating and superconducting states. This elusive phase, which is not consistent with current theories, is under heavy deliberations nowadays. We present an experimental study of the effect of high pressure on thin films of amorphous indium oxide. Our results show that pressure induces a series of transitions from a Bose insulator through a superconducting phase, metallic phases and finally to a conventional insulator. We suggest that our findings reaffirm the existence of a two-dimensional metal close to the SIT and show that its occurrence requires relatively strong coupling between regions that are weakly superconducting.