Interacting preformed Cooper pairs in resonant Fermi gases

K. B. Gubbels; H. T. C. Stoof

doi:10.1103/PhysRevA.84.013610

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Interacting preformed Cooper pairs in resonant Fermi gases

K. B. Gubbels, H. T. C. Stoof

DOI 10.1103/PhysRevA.84.013610 · Physical Review A

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Abstract

We consider the normal phase of a strongly interacting Fermi gas, which can have either an equal or an unequal number of atoms in its two accessible spin states. Due to the unitarity-limited attractive interaction between particles with different spin, noncondensed Cooper pairs are formed. The starting point in treating preformed pairs is the Nozières-Schmitt-Rink (NSR) theory, which approximates the pairs as being noninteracting. Here, we consider the effects of the interactions between the Cooper pairs in a Wilsonian renormalization-group scheme. Starting from the exact bosonic action for the pairs, we calculate the Cooper-pair self-energy by combining the NSR formalism with the Wilsonian approach. We compare our findings with the recent experiments by Harikoshi et al. [Science 327, 442 (2010)] and Nascimbène et al. [Nature (London) 463, 1057 (2010)], and find very good agreement. We also make predictions for the population-imbalanced case, which can be tested in experiments.