Superfluid densities in liquid helium films

Using the ring diagram approximation, the superfluid healing length and the superfluid density in two-dimensional helium film are explicitly evaluated. The theoretical results are in good agreement with experimental data obtained from resonance and other techniques in the range of temperatures from 0.1 to 1.50K. We have found that for thicknesses less than 3 atomic layers, the films can be treated as two dimensional. (author)