Quantum spin Hall physics with a topological Mott insulator

1/4 is the new 1/2: Interaction-induced Quantum Anomalous and Spin Hall Mott Insulators

Band structure for Hamiltonian in Eq. (

We introduce interactions into two general models for quantum spin hall physics and show that in the presence of strong interactions, the quarter-filled state instead exhibits the quantum spin anomalous hall effect with spin chern number a topological mott insulator is the underlying cause lying outside the standard topological classification.An intermediate interacting regime that exhibits a quantum anomalous hall effect emerges when the lower band is `flat'so that the interaction is large compared to the bandwidth but remains comparable to or smaller than the topological gap.This intermediate regime is consistent with the simultaneous observation in transition metal dichalcogenide moir{\'e} materials of a quantum anomalous hall phase at quarter filling and a quantum spin hall effect at half-filling.