The BCS-BEC Crossover and Superconductivity in a Lattice Fermion Model with Hard Core Repulsion

We considered the BCS-BEC crossover at T=0 in the framework of a lattice fermion model (the extended Hubbard model). We analyzed the case of on-site hard core repulsion (U=∞) and intersite attraction (W<0) in a 3D system with extended s-wave pairing symmetry. The mechanisms of density-driven and attraction-strength-driven crossover were analyzed. We obtained the ground state phase diagram. The analyzed quantities are: chemical potential, order parameter, coherence length, and fraction of condensed particles.