Momentum Distributions in3He-4He Mixtures

Abstract

We report variational calculations, in the framework of the HNC/FHNC theory, of the one-body density matrices and one-particle momentum distributions for 3He-4He mixtures at the zero temperature limit. The variational wave function used to describe the ground state of the mixture is a simple generalization of the trial wave functions for pure phases. We study the dependence on the 3He concentration (x3), of the condensate fraction of the 4He (n0 (4)) and the 3He pole strength (ZF) in the mixture along the isobar P = 0 atm. The differences between the results based on the Lennard-Jones and the Aziz potential are also discussed. It is found that the values of the condensate fraction do not depend strongly on the treatment of the 3He statistics. On the other hand, the Fermi character of the 3He is essential for the existence of the discontinuity in the 3He momentum distribution in the mixtures, the correlations between 4He and 3He being the main source of the small values of ZF. We predict a small increase of the 4He condensate fraction when x3 increases. This is a consequence of the fact that the total density of the mixture slightly decreases when the 3He concentration increases.