Two Types of Quasiparticles Excited in a Bose Gas

Abstract

We present a novel approach for investigating the superfluid liquid 4He based on the proper use of the nonideal Bose gas model for dilute hard spheres. The results show that the presence of a macroscopic number of condensate atoms leads to the existence of a nonphysical branch, corresponding to density excitations, in addition to the continuous branch of the phonon-maxon-roton excitation spectrum.

The condition of existence of the Bose–Einstein condensation in the superfluid liquid helium

“…whereĉ p andĉ + p are, respectively, the Bose-operators of densityquasiparticles presented in reference [9], which in turn are the Bose-operators of bosons used in expressions (6) and (7):…”

“…component in the inelastic neutron scattering intensity, the authors of papers [6][7][8] proposed the presence of collective modes in superfluid liquid 4 He, represented a density excitations. Thus the collective modes are represent as density quasiparticles [9]. Such density excitations and density quasiparticles appear because of the remaining density operator term that describes atoms above the condensate, a term which was neglected by Bogoliubov [3] when obtaining the dispersion curve for the single particle Bogoliubov excitations (Bogoliubov phonon-roton modes).…”