Phase diagram of fluid phases in (3)He-(4)He mixtures.

Abstract

Fluid parts of the phase diagram of (3)He-(4)He mixtures are obtained from a mean-field analysis of a suitable lattice gas model for binary liquid mixtures. The proposed model takes into account the continuous rotational symmetry O(2) of the superfluid degrees of freedom associated with (4)He and includes the occurrence of vacancies. This latter degree of freedom allows the model to exhibit a vapor phase and hence can provide the theoretical framework to describe the experimental conditions for measurements of tricritical Casimir forces in (3)He-(4)He wetting films.