Antiferromagnetism versus superconductivity in a tight-binding model with singlet nearest-neighbor pairing interaction

We study a tight-binding model with a singlet nearest-neighbor pairing interaction on a two-dimensional square lattice. In the strong coupling regime it undergoes an Ising-like antiferromagnetic phase transition 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 phasediagram. In the half-filled state, the system orders antiferromagnetically; otherwise superconductivity occurs and might coexist with antiferromagnetism. The implications on the specific heat and Pauli susceptibility are discussed. © 1994.