A study of the temperature dependence of single-particle and pair coherent condensate densities for the Bose liquid with the “depleted” single-particle Bose-Einstein condensate

In this paper we present the studies of the temperature dependence of single-particle and pair coherent condensate densities for the Bose liquid with the “depleted” single-particle Bose-Einstein condensate (BEC) at T ≠ 0. Our investigations are based on the field-theoretical Green functions approach. Superfluid state is described at T ≠ 0 on the basis of the use of empirical data for the first and second sound speeds. The structure of the superfluid state is studied taking into account the appearance of the normal component within non-zero temperatures and the branch of the second sound, where speed approaches zero at T → Tλ. The obtained temperature dependences of the single-particle and pair coherent condensate qualitatively agreed with the experimental data.