Low-temperature insulating phases of uniformly disordered two-dimensional superconductors

Abstract

Temperature and magnetic-field-dependent measurements of the longitudinal ${\mathit{R}}_{\mathit{x}\mathit{x}}$ and transverse ${\mathit{R}}_{\mathit{x}\mathit{y}}$ resistance of amorphous indium oxide thin-film superconductors reveal the presence of distinct insulating phases for sufficiently high disorder and/or magnetic field. For field-swept transitions at fixed disorder and low temperatures there is a critical field where ${\mathit{R}}_{\mathit{x}\mathit{x}}$ diverges and the superconductor is transformed into a Bose-glass insulator with localized Cooper pairs. At higher fields there is a second critical field where ${\mathit{R}}_{\mathit{x}\mathit{y}}$ appears to diverge, the pairs unbind, and localized single electrons characterizing a Fermi-glass insulator dominate.