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

We present variational calculations of the one-body density matrices and momentum distributions for He-3-He-4 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 He-3 concentration (x(3)) Of the He-4 condensate fraction (n(0)((4))) and of the He-3 pole strength (Z(F)) is studied along the P=0 isobar. At low He-3 concentrations, the computed He-4 condensate fraction is not significantly affected by the He-3 statistics. Despite the low x(3) values, Z(F) is found to be quite smaller than that of the corresponding pure He-3 because of the strong He-3-He-4 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 with respect to the pure-He-4 phase. [S0163-1829(97)03242-6].