Condensed Matter Physics, 2013, vol. 16, No. 1, 13603
DOI:10.5488/CMP.16.13603
arXiv:1303.5539
Title:
Role of singleparticle and pair condensates in Bose systems with arbitrary intensity of interaction
Author(s):

A.S. Peletminskii
(Akhiezer Institute for Theoretical Physics, NSC KIPT, 1 Akademicheskaya St., 61108 Kharkov, Ukraine)


S.V. Peletminskii
(Akhiezer Institute for Theoretical Physics, NSC KIPT, 1 Akademicheskaya St., 61108 Kharkov, Ukraine)


Yu.M. Poluektov
(Akhiezer Institute for Theoretical Physics, NSC KIPT, 1 Akademicheskaya St., 61108 Kharkov, Ukraine)

We study a superfluid Bose system with singleparticle and pair condensates on the basis of a halfphenomenological theory of a Bose liquid not involving the weakness of interparticle interaction. The coupled equations describing the equilibrium state of such system are derived from the variational principle for entropy. These equations are analyzed at zero temperature both analytically and numerically. It is shown that the fraction of particles in the singleparticle and pair condensates essentially depends on the total density of the system. At densities attainable in condensates of alkalimetal atoms, almost all particles are in the singleparticle condensate. The pair condensate fraction grows with increasing total density and becomes dominant. It is shown that at density of liquid helium, the singleparticle condensate fraction is less than 10% that agrees with experimental data on inelastic neutron scattering, Monte Carlo calculations and other theoretical predictions. The ground state energy, pressure, and compressibility are found for the system under consideration. The spectrum of singleparticle excitations is also analyzed.
Key words:
superfluidity, BoseEinstein condensation, singleparticle and pair condensates, quasiparticles, excitation spectrum
PACS:
67.10.Fj, 67.25.D, 67.85.Jk
