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 ∼$H^{\mathrm{-}2/3}$. 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.

• Received 5 August 1985

DOI:https://doi.org/10.1103/PhysRevLett.56.173