Exact solution to the Haldane-BCS-Hubbard model along the symmetric lines: Interaction-induced topological phase transition

We propose a Haldane-BCS-Hubbard model on a honeycomb lattice which is composed of two copies of the Haldane model of the quantum anomalous Hall effect, an equal-spin pairing term, and an on-site Hubbard interaction term. For any interaction strength, this model is exactly solvable along the symmetric line where the hopping and pairing amplitudes are equal to each other. The ground state of the Haldane-BCS-Hubbard model is a topological superconducting state at weak interaction with two chiral Majorana edge states. A strong interaction drives the system across a topological quantum phase transition to a topologically trivial superconductor. A Z(2) symmetry of the Hamiltonian, which is a composition of the bond-centered inversion and a gauge transformation, is spontaneously broken by the interaction, resulting in a finite antiferromagnetic order in the y direction.