Antiferromagnetism vs. Superconductivity in a Tight-Binding Model with Singlet Nearest-Neighbour Pairing Interaction

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Abstract
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 Néel 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.