Conserving Gapless Mean-Field Theory of a Multi-Component Bose-Einstein Condensate
- Resource Type
- Working Paper
- Authors
- Kondo, Yoshiyuki; Kita, Takafumi
- Source
- J. Phys. Soc. Jpn. 76, 024008 (2007)
- Subject
- Condensed Matter - Statistical Mechanics
- Language
We develop a mean-field theory for Bose-Einstein condensation of spin-1 atoms with internal degrees of freedom. It is applicable to nonuniform systems at finite temperatures with a plausible feature of satisfying the Hugenholtz-Pines theorem and various conservation laws simultaneously. Using it, we clarify thermodynamic properties and the excitation spectra of a uniform gas. The condensate is confirmed to remain in the same internal state from T=0 up to $T_{c}$ for both antiferromagnetic and ferromagnetic interactions. The excitation spectra of the antiferromagnetic (ferromagnetic) interaction are found to have only a single gapless mode, contrary to the prediction of the Bogoliubov theory where three (two) of them are gapless. We present a detailed discussion on those single-particle excitations in connection with the collective excitations.
Comment: 8 pages, 7 figures Minor errors removed