Quantum anomalous Hall effect in flat bands with weak ferrimagnetism
Phys. Rev. B 114, 105117 – Published 14 August, 2026
DOI: https://doi.org/10.1103/2sh7-b44x
Abstract
The quantum anomalous Hall effect has been widely explored in both ferromagnetic and antiferromagnetic systems. Here, we propose an interaction-driven weak ferrimagnetic quantum anomalous Hall effect emerging in the Fermi-Hubbard model on a dice lattice with weak spin-orbit coupling. Based on exact diagonalization calculations, the many-body ground state possesses a Chern number of or 6. In the absence of local spin and orbital magnetic moments, time-reversal symmetry breaking in the ground state is evidenced by chiral edge currents. The strong correlation effects in the half-filled flat bands lead to a well-defined first excitation gap and a clear insulating gap, ensuring robustness against thermal fluctuations and external perturbations. The interplay between spin-orbit coupling and Hubbard interaction allows the tunability of various magnetic ground states, generating a rich phase diagram with competing ferrimagnetic, weak ferrimagnetic, and paramagnetic orders.
