Single-particle excitations in the BCS-BEC crossover region II: Broad Feshbach resonance

Abstract

We apply the formulation developed in a recent paper [Y. Ohashi and A. Griffin, Phys. Rev. A {\bf 72}, 013601, (2005)] for single-particle excitations in the BCS-BEC crossover to the case of a broad Feshbach resonance. At T=0, we solve the Bogoliubov-de Gennes coupled equations taking into account a Bose condensate of bound states (molecules). In the case of a broad resonance, the density profile $n(r)$, as well as the profile of the superfluid order parameter $\tilde{\Delta }(r)$, are spatially spread out to the Thomas-Fermi radius, even in the crossover region. This order parameter $\tilde{\Delta }(r)$ suppresses the effects of low-energy Andreev bound states on the rf-tunneling current. As a result, the peak energy in the rf-spectrum is found to occur at an energy equal to the superfluid order parameter $\tilde{\Delta }(r=0)$ at the center of the trap, in contrast to the case of a narrow resonance, and in agreement with recent measurements. The LDA is found to give a good approximation for the rf-tunneling spectrum.

14 pages, 8 figures

References in corpus (4)

• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Crossover from a molecular Bose-Einstein condensate to a degenerate Fermi gas
• Condensate Fraction of a Fermi Gas in the BCS-BEC Crossover
• Single-particle excitations in a trapped gas of Fermi atoms in the BCS-BEC crossover region

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• Adiabatic Phase Diagram of an Ultracold Atomic Fermi Gas with a Feshbach Resonance
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