Topological phase in the extended Haldane-Hubbard model with sublattice-dependent repulsion

TL;DR

This paper investigates the phase diagram of an extended Haldane-Hubbard model with sublattice-dependent repulsion, revealing a topologically nontrivial phase with Chern number 1 driven by on-site interaction imbalance.

Contribution

It demonstrates a novel route to topological phases by tuning on-site interactions alone, without sublattice potentials, using ED and mean-field methods.

Findings

Identification of a C=1 topological phase driven by interaction imbalance

Observation of antiferromagnetic correlations in the topological phase

Spontaneous SU(2) symmetry breaking in the phase

Abstract

We study the ground-state phase diagram of the half-filled extended Haldane-Hubbard model on the honeycomb lattice with sublattice-dependent on-site repulsion ($U_{\text{A/B}}$) using the exact diagonalization (ED) and mean-field (MF) methods. The resulting phase diagram shows that there is a topologically nontrivial phase with the Chern number $C=1$, emerging via the development of the imbalance between $U_{\text{A}}$ and $U_{\text{B}}$. In this phase, the antiferromagnetic correlations are observed in the ED calculation, in line with the finite antiferromagnetic order obtained by the MF method. The spontaneous symmetry breaking of SU(2) spin rotation in the phase is also identified in the MF level. Distinct from previous studies in which the exotic $C=1$ phase relies on the interplay between sublattice-dependent potentials and electronic interactions, our paper presents an alternative way by solely tuning the on-site interactions.