Nonequilibrium-enhanced supercurrents in short superconducting weak links

Abstract

We have measured the low-voltage footlike features of the $I\ensuremath{-}V$ characteristics of tin variablethickness superconducting microbridges as a function of temperature. We find these to be consistent with a voltage-dependent enhancement of the supercurrent induced by the disequilibrium of the quasiparticles during the Josephson cycle. We discuss the physical origin of this effect and the more-specific microscopically based models of Golub and of Aslamazov and Larkin. We find the predictions of these models to be complementary, and in good agreement with many aspects of our experimental results.