Antiferromagnetism vs. Superconductivity in a tight-binding model with singlet nearest-neighbour pairing interaction

We study a tight-binding model with a singlet nearest-neighbour pairing interaction in two dimensions. In the strong-coupling limit the system undergoes an antiferromagnetic phase transition with a finite Neel temperature for all fillings. For this reason we include both an antiferromagnetic and a superconducting order parameter within the symmetry-broken Hartree-Fock approximation and derive the self-consistent phase diagram. In the half-filled state, the system orders antiferromagnetically; otherwise superconductivity occurs and might coexist with antiferromagnetism. The implications on the specific heat and the Pauli susceptibility are discussed. © 1995 Les Editions de Physique.