Pair excitations, collective modes, and gauge invariance in the BCS–Bose-Einstein crossover scenario
Pair excitations, collective modes, and gauge invariance in the BCS–Bose-Einstein crossover scenario
In this paper we study the BCS Bose-Einstein condensation (BEC) crossover scenario within the superconducting state, using a T-matrix approach which yields the ground state proposed by Leggett. Here we extend this ground state analysis to finite temperatures T and interpret the resulting physics. We find two types of bosoniclike …