Inhomogeneous broadening and the Kosterlitz-Thouless transition

Torsional-oscillator studies of very thin He4 films have found nonuniversal behavior of the superfluid response as a function of coverage. The temperature width of the superfluid transition region is nonmonotonic in the areal density n and exhibits cusplike variations at half of the layering period. We explore the assumption that this additional broadening is caused by macroscopic inhomogeneities in the substrate potential; such a theory for …