Intrinsic Critical Velocity of a Superfluid

Abstract

A fluctuation theory of the intrinsic critical velocity of a superfluid near the lambda point is developed in analogy with the droplet model of condensation of a supersaturated vapor. For the superfluid, vortex rings play the role of critical droplets in homogeneously nucleating transitions to states of lower superflow. A quantitative estimate is in reasonable agreement with recent experiments on helium.