ANTIFERROMAGNETISM VS SUPERCONDUCTIVITY IN A TIGHT-BINDING MODEL WITHSINGLET NEAREST-NEIGHBOR PAIRING INTERACTION

We study a tight-binding model with a singlet nearest-neighbour pairin g interaction in two dimensions. In the strong-coupling limit the syst em undergoes an antiferromagnetic phase transition with a finite Neel temperature for all fillings. For this reason we include both an antif erromagnetic and a superconducting order parameter within the symmetry -broken Hartree-Fock approximation and derive the self-consistent phas e diagram. In the half-filled state, the system orders antiferromagnet ically; otherwise superconductivity occurs and might coexist with anti ferromagnetism. The implications on the specific heat and the Pauli su sceptibility are discussed.