JOSEPHSON PROPERTIES OF NB CU MULTILAYERS

The self-consistent equations, which have been derived recently as a m icroscopic model for the crossover between BCS superconductivity and B ose-Einstein condensation in a three-dimensional interacting Fermi sys tem [R. Hausmann, Z Phys B 91, 291, (1993)[, are solved nume rically by repeated Fourier transformation. We find a superfluid trans ition temperature T(c) which increases monotonically with increasing a ttractive coupling strength. Furthermore, we determine the chemical po tential Μ, the fermion distribution function n(k), and the complex effective mass 2m(*) of the fermion pairs T=T(c). The bound fermio n pairs cause a power-law tail ∼k(-4) in n(k) for large k and beha ve as short-living quasi-particles in the crossover region, which is i ndicated by a large imaginary part of 2m(*).