Superfluid density of 4He films adsorbed on slip-cast powder

Abstract

The superfluid density of thin 4He films adsorbed in slip-cast samples of 500A˚diameter Al 2O 3 powder has been measured using a torsion oscillator technique. Calibration of the data shows that the superfluid transition is controlled by the universal Kosterlitz-Thouless line, as found in previous third sound studies. There is no abrupt “jump” in the superfluid density at that point, but a smooth transition that is broadened by the finite grain size of the powder. The slip-cast sample is much more homogenous than previous packed powder samples, but near T c there is still a rounded tail to the superfluid density of about 10–15 mK.