Observation of a new universal resistive behavior of two-dimensional superconductors in a magnetic field

Abstract

A new universal behavior has been observed in the zero-bias resistance of two-dimensional superconducting films of amorphous Mo-Ge in a perpendicular magnetic field. The behavior is thermally activated, with a single field-dependent activation energy \ensuremath{\sim}${H}^{\mathrm{\ensuremath{-}}2/3}$. Additionally, a continuous crossover between two different limiting behaviors is observed, with no evidence for a sharp phase transition. Although the observed universal behavior appears to depend crucially upon the existence of pinning, it is qualitatively different from conventional flux-flow or depinning phenomena.