Superfluidity in Thin Helium Four Films

Abstract

I wish to discuss in these lectures the experimental aspects of superfluidity in thin films of adsorbed helium. I will be concerned mainly with those films ranging from about five atomic layers down to the thinnest which show evidence of superfluidity. I shall begin with a brief review of the superfluid properties of bulk helium as these ideas are well understood and form the conceptual basis for our understanding of superfluidity in films. The experimental methods used for observation of the superfluid properties of films will then be surveyed. In the final lecture, I will discuss the nature of the superfluid transition in films, and, in particular, the evidence for both two and three dimensional superfluid phase transitions in films, depending on the topology of the adsorption substrate.