Abstract
A self-consistent theory is derived to describe the BCS–Bose-Einstein-condensate crossover for a strongly interacting Fermi gas with a Feshbach resonance. In the theory the fluctuation of the dressed molecules, consisting of both preformed Cooper pairs and “bare” Feshbach molecules, has been included within a self-consistent -matrix approximation, beyond the Nozières and Schmitt-Rink strategy considered by Ohashi and Griffin. The resulting self-consistent equations are solved numerically to investigate the normal-state properties of the crossover at various resonance widths. It is found that the superfluid transition temperature increases monotonically at all widths as the effective interaction between atoms becomes more attractive. Furthermore, a residue factor of the molecule’s Green function and a complex effective mass have been determined to characterize the fraction and lifetime of Feshbach molecules at . Our many-body calculations of agree qualitatively well with recent measurments of the gas of atoms near the broad resonance at . The crossover from narrow to broad resonances has also been studied.
- Received 18 May 2005
DOI:https://doi.org/10.1103/PhysRevA.72.063613
©2005 American Physical Society