Multiple condensed phases in attractively interacting Bose systems

TL;DR

This paper explores phase transitions in an attractive Bose gas, revealing multiple condensed phases and the impact of interactions on the transition pathways, including a BCS-like phase and Bose-Einstein condensation.

Contribution

It introduces a corrected T-matrix approach to study finite-range interactions in Bose gases, identifying multiple phases and transition mechanisms.

Findings

Discovery of a BCS-like phase with a gaped dispersion

Identification of a critical density where Bose-Einstein condensation occurs

Observation of a possible first order transition preventing certain quantum phase transitions

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 BCS-like phase with a gaped 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.