SUPERFLUIDITY IN 2-DIMENSIONS - A THERMAL-CONDUCTIVITY STUDY OF HE-4 AND HE-3-HE-4 MIXTURE FILMS

We review measurements of the thermal transport of He-4 films and He-3-He-4 mixture films near the superfluid transition. These measurements were performed on helium films of thickness ranging from 12 to 156 angstrom and mixture films with He-3 concentration up to 2%. The superfluid transition temperature for these films ranged from 1.2 to 2.2 K. We discuss universal features of the data as well as the behavior of the ratio of the vortex diffusion constant to vortex core-parameter, the sharpness of the transition and the superfluid transition temperature as a function of thickness and concentration. We also describe new experiments that will contribute to a better understanding of the observed behavior.