Number of closed-channel molecules in the BEC-BCS crossover

Felix Werner (1) , Leticia Tarruell (1) , Yvan Castin (1)

1 LKB (Lhomond) - Laboratoire Kastler Brossel

Using a two-channel model, we show that the number of closed channel molecules in a two-component Fermi gas close to a Feshbach resonance is directly related to the derivative of the energy of the gas with respect to the inverse scattering length. We extract this quantity from the fixed node Monte-Carlo equation of state and we compare to the number of closed channel molecules measured in the Rice experiment with lithium [Partridge et al., Phys. Rev. Lett. 95, 020404 (2005)]. We also discuss the effect of a difference between the trapping potentials seen by a closed-channel molecule and by an open-channel pair of atoms in terms of an effective position-dependent scattering length.

Mots clés: BEC-BCS crossover; Feshbach resonance

Domaines: Autre [cond-mat.other]

Felix Werner, Leticia Tarruell, Yvan Castin. Number of closed-channel molecules in the BEC-BCS crossover. The European Physical Journal B: Condensed Matter and Complex Systems, 2009, 68, pp.401. ⟨hal-00292255v3⟩