We present a mean-field model to describe condensates in the BEC-BCS crossover regime based on pairs of fermionic atoms. By introducing an effective potential, the mean-field equation allows us to calculate the chemical potential, the equation of states, and the atomic correlation function. The results agree surprisingly well with recent many-body calculations. We show that the smooth crossover from the bosonic mean-field repulsion between molecules to the Fermi pressure among atoms is associated with the evolution of the atomic correlation function.

• Received 25 September 2004

DOI:https://doi.org/10.1103/PhysRevA.72.041601