Crossover from Weak- to Strong-Coupling Superconductivity and to Normal   State with Pseudogap
  For an electron gas with a $ \delta $-function attraction we investigate the crossover from weak-coupling to strong-coupling superconductivity as well as normal state near the temperature $T^*$, at which the strong coupling produces a pseudogap in the energy spectrum due to the binding of electron pairs. We present curves for the behavior of the superconductive transition temperature, the gap formation temperature, the gap size and several thermodynamic quantities as functions of coupling strength and temperature, both in two and three dimensions. 
E. Babaev and H. Kleinert