Publication at Faculty of Mathematics and Physics |
2010
Abstract
We investigate a Bose gas with finite-range interaction using a scheme to eliminate unphysical processes in the T-matrix approximation. In this way the corrected T-matrix becomes suitable to calculate properties below the critical temperature.
For attractive interaction, an Evans–Rashid transition occurs between a quasi-ideal Bose gas and a Bardeen–Cooper–Schrieffer-like phase with a gap dispersion. The gap decreases with increasing density and vanishes at a critical density where the single-particle dispersion becomes linear for small momenta, indicating Bose–Einstein condensation.
The investigation of the pressure shows, however, that the mentioned quantum phase transitions might be inaccessible due to a preceding first-order transition.