Effective c-number field of a superfluid without a condensate

Journal Article · Thu Aug 01 04:00:00 EDT 1985 · Sov. Phys. - JETP (Engl. Transl.); (United States)

OSTI ID:6097030

Nepomnyashchii, Y A

It has been shown previously (Sov. Phys. JETP 58, 722 (1983)) that the ''exotic'' properties of a Bose condensate (of the quasiaverage psi = ), which stem from the anomalous fluctuations in psi caused by phase degeneracy, rule out the identification of a ''microscopic'' basis of a phenomenological c-number field of a superfluid with this condensate. A microscopic definition of the c-number field as a quasiaverage is written by replacing the original field operator psi-circumflex by an effective operator psi-circumflex. The need for this replacement is even more obvious when the fluctuations resulting from the degeneracy destroy the condensate entirely: psi = 0 (the superfluidity, either two-dimensional (T>0) or one-dimensional (T = 0), of the Bose system is retained). When the condensate vanishes, psi = 0, the effective field psi-tilde = is conserved. Furthermore, regardless of the presence of a condensate, this field can be represented as the wave function of some effective condensate of quasiparticles which determines the ground state of the superfluid. At T>0, this field, along with the thermal excitations, determines the density matrix of the superfluid. The effective condensate not only reveals the quantum-mechanical nature of the c-number field of a superfluid, in terms of a macroscopically filled one-particle level (by analogy with an ideal Bose gas and ordinary ''classical'' fields) but also constitutes a necessary and sufficient condition for superfluidity.

• Research Organization: Perm' State University
• OSTI ID: 6097030
• Journal Information: Sov. Phys. - JETP (Engl. Transl.); (United States), Journal Name: Sov. Phys. - JETP (Engl. Transl.); (United States) Vol. 62:2; ISSN SPHJA
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BOSE-EINSTEIN CONDENSATION
FLUCTUATIONS
FUNCTIONS
SUPERFLUIDITY
VARIATIONS
WAVE FUNCTIONS