Momentum distributions in 3He-4He liquid mixtures

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 (x3) of the 4He condensate fraction (n0(4)) and of the 3He pole strength (ZF) is studied along the P=0 isobar. At low 3He concentrations, the computed 4He condensate fraction is not significantly affected by the 3He statistics. Despite the low x3 values, ZF 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 ρ. A small increase of n0(4) along x3 is found, which is mainly due to the decrease of ρ with respect to the pure-4He phase. copyright 1997 The American Physical Society