Topological phase transitions in the repulsively interacting Haldane-Hubbard model

TL;DR

This paper investigates the phase diagram of the repulsive Haldane-Hubbard model, revealing new topological phases and phase transitions driven by interactions and sublattice potential differences.

Contribution

It identifies a novel C=1 quantum Hall phase and explains its origin through spontaneous symmetry breaking, expanding understanding of topological phases in correlated systems.

Findings

Discovery of a C=1 quantum Hall phase

Identification of a Mott insulating phase with C=0

Explanation of the C=1 phase via symmetry breaking

Abstract

Using dynamical mean-field theory and exact diagonalization we study the phase diagram of the repulsive Haldane-Hubbard model, varying the interaction strength and the sublattice potential difference. In addition to the quantum Hall phase with Chern number $C=2$ and the band insulator with $C=0$ present already in the noninteracting model, the system also exhibits a $C=0$ Mott insulating phase, and a $C=1$ quantum Hall phase. We explain the latter phase by a spontaneous symmetry breaking where one of the spin-components is in the Hall state and the other in the band insulating state.