Valley-Polarized Quantum Anomalous Hall State in Moire MoTe2/WSe2 Heterobilayers

Moire heterobilayer transition metal dichalcogenides (TMDs) emerge as an ideal system for simulating the single-band Hubbard model and interesting correlated phases have been observed in these systems. Nevertheless, the moire bands in heterobilayer TMDs were believed to be topologically trivial. Recently, it was reported that both a quantum valley Hall insulating state at filling nu = 2 (two holes per moire unit cell) and a valley-polarized quantum anomalous Hall state at filling nu = 1 were observed in AB stacked moire MoTe2/WSe2 heterobilayers. However, how the topologically nontrivial states emerge is not known. In this Letter, we propose that the pseudomagnetic fields induced by lattice relaxation in moire MoTe2/WSe2 heterobilayers could naturally give rise to moire bands with finite Chern numbers. We show that a time-reversal invariant quantum valley Hall insulator is formed at full filling nu = 2, when two moire bands with opposite Chern numbers are filled. At half filling nu = 1, the Coulomb interaction lifts the valley degeneracy and results in a valley-polarized quantum anomalous Hall state, as observed in the experiment. Our theory identifies a new way to achieve topologically nontrivial states in heterobilayer TMD materials.