Influence of the superfluid transition on the adsorption of thin helium films

Abstract

An approach to the calculation of the chemical potential of a thin helium film in equilibrium with the vapor is proposed. In the calculation of the chemical potential the surface layer of helium atoms in contact with the vapor is treated as a two-dimensional system. The chemical potential of superfluid helium is approximated by the chemical potential of an ideal two-dimensional Bose gas, while the chemical potential of normal helium contains an additional, temperature-dependent term. This approach leads to the prediction that the thickness of the film will increase at the transition to the superfluid state. It is also predicted that a coexistence of normal and superfluid films of different thickness is possible under certain conditions.