Europhys. Lett.
Volume 69, Number 5, March 2005
Page(s) 713 - 718
Section General
Published online 02 February 2005
Europhys. Lett., 69 (5), pp. 713-718 (2005)
DOI: 10.1209/epl/i2004-10412-2

Broad vs. narrow Fano-Feshbach resonances in the BCS-BEC crossover with trapped Fermi atoms

S. Simonucci, P. Pieri and G. C. Strinati

Dipartimento di Fisica, UdR INFM, Università di Camerino - I-62032 Camerino, Italy

received 12 November 2004; accepted 23 December 2004
published online 2 February 2005

With reference to the broad and narrow Fano-Feshbach resonances of $\chem{{}^{6}Li}$ at about 822$\un{G}$ and 543$\un{G}$, we show that for the broad resonance a molecular coupled-channel calculation can be mapped with excellent accuracy onto an effective single-channel problem with a contact interaction. This occurs for a wide enough range of the magnetic field that the full BCS-BEC crossover can be realized with a typical trap. For the narrow resonance, the mapping onto a single-channel problem and the realization of the BCS-BEC crossover are restricted to too narrow a range of the magnetic field to obtain them in practice. A general criterion is also formulated for deciding whether the BCS-BEC crossover can be exhausted within the single-channel model for any specific Fano-Feshbach resonance. In this way, the BCS-BEC crossover for Fermi atoms with the broad resonance is placed on the same footing as the corresponding crossover for different physical systems.

03.75.Ss - Degenerate Fermi gases.
34.50.Pi - State-to-state scattering analyses.
03.75.Hh - Static properties of condensates; thermodynamical, statistical and structural properties.

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