Quantum anomalous Hall effect from intertwined moire bands

Electron correlation and topology are two central threads of modern condensed matter physics. Semiconductor moire materials provide a highly tuneable platform for studies of electron correlation(1-12). Correlation-driven phenomena, including the Mott insulator(2-5), generalized Wigner crystals(2,6,9), stripe phases(10) and continuous Mott transition(11,12), have been demonstrated. However, non-trivial band topology has remained unclear. Here we report the observation of a quantum anomalous Hall effect in AB-stacked MoTe2 /WSe2 moire heterobilayers. Unlike in the AA-stacked heterobilayers(11), an out-of-plane electric field not only controls the bandwidth but also the band topology by intertwining moire bands centred at different layers. At half band filling, corresponding to one particle per moire unit cell, we observe quantized Hall resistance, h/e(2) (with h and e denoting the Planck's constant and electron charge, respectively), and vanishing longitudinal resistance at zero magnetic field. The electric-field-induced topological phase transition from a Mott insulator to a quantum anomalous Hall insulator precedes an insulator-to-metal transition. Contrary to most known topological phase transitions(13), it is not accompanied by a bulk charge gap closure. Our study paves the way for discovery of emergent phenomena arising from the combined influence of strong correlation and topology in semiconductor moire materials.

Automated summary

This study reveals the observation of quantum anomalous Hall effect in AB-stacked MoTe2/WSe2 moire heterobilayers, which exhibits unique band topology characteristics. At half band filling, quantized Hall resistance and vanishing longitudinal resistance are observed, indicating a topological phase transition induced by an out-of-plane electric field.