Single-particle excitations in a trapped gas of Fermi atoms in the BCS-BEC crossover region. II. Broad Feshbach resonance

We apply the formulation developed in a recent paper [Y. Ohashi and A. Griffin, Phys. Rev. A 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 Δ(r), are spatially spread out to the Thomas-Fermi radius, even in the crossover region. This order parameter Δ(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 Δ(r=0) at the center of the trap, in contrast to the case of a narrow resonance, and in agreement with recent measurements. The local density approximation is found to give a good approximation for the rf-tunneling spectrum.