Momentum distribution in 3He-4He liquid mixtures

Abstract

We present variational calculations of the one-body density matrices and momentum distributions for 3 H e − 4 He 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 3 He concentration ( x 3 ) of the 4 He condensate fraction ( n ( 4 ) 0 ) and of the 3 He pole strength ( Z F ) is studied along the P = 0 isobar. At low 3 He concentrations, the computed 4 He condensate fraction is not significantly affected by the 3 He statistics. Despite the low x 3 values, Z F is found to be quite smaller than that of the corresponding pure 3 He because of the strong 3 H e − 4 He correlations and of the overall, large total density ρ. A small increase of n ( 4 ) 0 along x 3 is found, which is mainly due to the decrease of ρ with respect to the pure- 4 He phase.