TACKLING FLUCTUATION CORRECTIONS IN THE BEC/BCS CROSSOVER AT NONZERO TEMPERATURES
The investigation of superfluid atomic Fermi gases in the regime of strong interactions is conveniently investigated with the path-integral method at temperature zero, or at the critical temperature where the gap vanishes, by taking particle-pair or hole-pair fluctuations into account. Here, we also take the particle-hole excitations into account, which is important to investigate intermediate temperatures. The additional terms in the fluctuation propagator are identified, and a contour integral representation is used to calculate the contribution of these terms to the free energy and to the density of noncondensed fermions.