Kosterlitz-Thouless Superfluid Transition for Helium in Packed Powders

Abstract
A model is presented for the Kosterlitz-Thouless superfluid transition of helium films adsorbed on the surface of a sphere. As the sphere diameter is reduced to grain sizes used in experiments the sharp "jump" to zero of the areal superfluid density is broadened and becomes continuous. The model is applied to third-sound measurements in packed alumina powders, and values of the core energy and core radius of the paired vortices are extracted.