Particle-hole fluctuations in the BCS-BEC Crossover
arXiv:0808.0150 · doi:10.1103/PhysRevB.78.174528
Abstract
The effect of particle-hole fluctuations for the BCS-BEC crossover is investigated by use of functional renormalization. We compute the critical temperature for the whole range in the scattering length . On the BCS side for small negative we recover the Gorkov approximation, while on the BEC side of small positive the particle-hole fluctuations play no important role, and we find a system of interacting bosons. In the unitarity limit of infinite scattering length our quantitative estimate yields . We also investigate the crossover from broad to narrow Feshbach resonances -- for the later we obtain for . A key ingredient for our treatment is the computation of the momentum dependent four-fermion vertex and its bosonization in terms of an effective bound-state exchange.
11 pages, 6 figures. Reference added
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