Kosterlitz-Thouless behavior and scaling in superfluid helium films

The results of a series of measurements of Kosterlitz-Thouless behavior in helium films are presented. Use is made of high Q piezoelectric crystals so as to probe the phenomena in a single flat substrate geometry at high frequencies. Variations of the superfluid density and dissipation in the vicinity of the transition were measured. Results are compared with a comprehensive numerical calculation in which finite size scaling effects are explicitly introduced. A consistent picture for the dependence of critical thickness on temperature is obtained.