Mean-Field vs Monte-Carlo equation of state for the expansion of a Fermi superfluid in the BCS-BEC crossover

Abstract

The equation of state (EOS) of a Fermi superfluid is investigated in the BCS-BEC crossover at zero temperature. We discuss the EOS based on Monte-Carlo (MC) data and asymptotic expansions and the EOS derived from the extended BCS (EBCS) mean-field theory. Then we introduce a time-dependent density functional, based on the bulk EOS and Landau's superfluid hydrodynamics with a von Weizsäcker-type correction, to study the free expansion of the Fermi superfluid. We calculate the aspect ratio and the released energy of the expanding Fermi cloud showing that MC EOS and EBCS EOS are both compatible with the available experimental data of ${}^6$Li atoms. We find that the released energy satisfies an approximate analytical formula that is quite accurate in the BEC regime. For an anisotropic droplet, our numerical simulations show an initially faster reversal of anisotropy in the BCS regime, later suppressed by the BEC fluid.

13 pages, 3 figures, presented to the 15th International Laser Physics Workshop (Lausanne, July 24-28, 2006); to be published in Laser Physics

References in corpus (3)

• Weakly bound dimers of fermionic atoms
• Collective modes and ballistic expansion of a Fermi gas in the BCS-BEC crossover
• Expansion of a Fermi Cloud in the BCS-BEC Crossover

Cited by in corpus (6)

• Superfluid Bose-Fermi mixture from weak-coupling to unitarity
• DC Josephson Effect with Fermi gases in the Bose-Einstein regime
• Nonlinear Schroedinger equation for a superfluid Bose gas from weak coupling to unitarity: Study of vortices
• Condensate Fraction of a Two-Dimensional Attractive Fermi Gas
• Hydrodynamics of Bose and Fermi superfluids at zero temperature: the superfluid nonlinear Schrodinger equation
• DC and AC Josephson effects with superfluid Fermi atoms across a Feshbach resonance