PHASE SLIPPAGE IN THIN SUPERFLUID FILMS

We have extended the Ambegaokar, Halperin, Nelson and Siggia theory of vortex de-pairing in two-dimensional superfluids to describe how the current of free vortices varies with superfluid velocity, v(s), in the steady state, for temperatures just above the Kosterlitz-Thouless transition. To do so we have solved exactly the Fokker-Planck equation which describes the current of vortices produced at one edge of the film. We are able to calculate how a persistent current decays, and the thermal resistance o a film as a function of heater power. Superconducting films are considered as a charged, two-dimensional superfluid, and the theory is applied to them.