First-order pairing transition and phase separation in the attractive Hubbard model

The normal state properties of the Hubbard model are studied by means of the Dynamical Mean-Field Theory. Even in the gauge-symmetric subspace, a first-order transition occurs between a Fermi-liquid phase and a strong-coupling bound-pairs phase, which can be thought as a "disordered" superconductor. The transition is of first order for all densities different from n = 1, and it is accompanied by a region of phase separation between the two phases at different densities. RI Grilli, Marco/C-6309-2009; Capone, Massimo/A-7762-2008