Title: THE PROPERTIES OF THIN $^3$He-$^4$He SUPERFLUID FILMS
Author(s): R.H.Anderson, M.D.Miller (Department of Physics, Washington State University, Pullman, WA 99164-2814 USA)

Thin $^{3}$He-$^{4}$He physisorbed films are examples of strongly interacting, quasi two-dimensional, fermion-boson mixture systems. The properties of the mixture systems can be tuned by changing the substrate or the $^{4}$He film thickness. In this paper, we discuss the ground-state and magnetic ground-state of the $^{3}$He subsystem and also the interactions between the excitations of the $^{4}$He superfluid film with the single-particle excitations of the adsorbed $^{3}$He. The ground-state of the $^{3}$He system is calculated using a model for the $^{3}$He-$^{3}$He effective interaction in the static $^{4}$He film which explicitly includes the effective interaction due to exchange of virtual film excitations (ripplons). This latter effective interaction is evaluated in the random phase approximation and is shown \textit {not} to be capable of causing the $^{3}$He system to be self-bound. We discuss the evidence from magnetization, third sound and heat capacity measurements that the $^{3}$He first transverse excited state is being occupied prior to monolayer completion.

Key words: superfluid films, $^{3}$He-$^{4}$He mixtures, third sound, ripplons
PACS: 67.70.+n, 67.60.Fp, 64.30.+t