Momentum distributions in ^3He-^4He liquid mixtures

TL;DR

This paper uses variational calculations within correlated basis functions theory to analyze how ^3He-^4He liquid mixtures' momentum distributions and condensate fractions depend on ^3He concentration at zero temperature.

Contribution

It provides the first detailed variational analysis of the momentum distributions and condensate fractions in ^3He-^4He mixtures considering two- and three-body correlations.

Findings

^4He condensate fraction is stable at low ^3He concentration.

^3He pole strength Z_F is significantly reduced due to correlations.

Small increase in ^4He condensate fraction with ^3He concentration.

Abstract

We present variational calculations of the one-body density matrices and momentum distributions for ^3He-^4He mixtures in the zero temperature limit, in the framework of the correlated basis functions theory. The ground-state wave function contains two- and three-body correlations and the matrix elements are computed by (Fermi)Hypernetted Chain techniques. The dependence on the ^3He concentration (x_3) of the ^4He condensate fraction $(n_0^{(4)})$ and of the ^3He pole strength (Z_F) is studied along the P=0 isobar. At low ^3He concentration, the computed ^4He condensate fraction is not significantly affected by the ^3He statistics. Despite of the low x_3 values, Z_F is found to be quite smaller than that of the corresponding pure ^3He because of the strong ^3He-^4He correlations and of the overall, large total density \rho. A small increase of $n_0^{(4)}$ along x_3 is found, which is mainly due to the decrease of \rho respect to the pure ^4He phase.