In this paper we present predictions for thermodynamic and transport properties of a BCS to Bose-Einstein crossover theory, below $T_c$, which satisfies the reasonable constraints that it yields (i) the Leggett ground state and (ii) BCS theory at weak coupling and all temperatures $T$. The nature of the strong coupling limit is inferred, along with the behavior of the Knight shift, superfluid density, and specific heat. Comparisons with existing data on short coherence length superconductors, such as organic and high $T_c$ systems, are presented, which provide some support for the present picture.

• Received 2 November 1999

DOI:https://doi.org/10.1103/PhysRevLett.85.2801