Unified symmetry-breaking theory of Bose-Einstein condensation in superfluids
- Laboratorio Nacional de Computacao Cientifica, Caixa Postal 56018, 22290 Rio de Janeiro, Rio de Janeiro, Brazil (BR)
The usual symmetry-breaking procedures for Bose condensed systems, namely, the Bogoliubov prescription, the symmetry-breaking term added to the Hamiltonian, and the canonical shift transformation are unified into a single formalism. By taking into account the condensate reservoir as a source and sink of excited particles, exact Ward identities are solved in the shielded-potential approximation. A relationship between the condensate density {ital n}{sub 0} and the superfluid density {ital n}{sub {ital S}} is obtained in closed form. It is shown that the Bogoliubov prescription yields {ital n}{sub 0}{congruent}{ital n}{sub {ital S}} and {ital nU}{sub 0}{much lt}{vert bar}{mu}{vert bar}, where {ital n} is the total density, {ital U}{sub 0} the interaction constant, and {mu} the chemical potential. On the other hand, for the canonical shift transformation one has {ital n}{sub 0}{much lt}{ital n}{sub {ital S}} and {ital nU}{sub 0}{much gt}{vert bar}{mu}{vert bar}. The latter, applied to superfluid {sup 4}He at saturated vapor pressure, gives excellent agreement between theory and experiment, without any adjustable parameter. The condensate density turns out to be strongly dependent on pressure as observed experimentally. The formalism provides in a natural way a consistent description of Bose systems in arbitrary {ital D}-dimensional space.
- OSTI ID:
- 5675471
- Journal Information:
- Physical Review, B: Condensed Matter; (USA), Vol. 43:10; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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