Our results are consistent with the universal critical theory of a continuous Mott transition in two dimensions4,23. This signals an abundance of low-energy spinful excitations on the insulating side that is further corroborated by the Pomeranchuk effect observed on the metallic side. We also observe a smooth evolution of the magnetic susceptibility across the MIT and no evidence of long-range magnetic order down to ~5% of the Curie–Weiss temperature. The existence of quantum criticality is supported by the scaling collapse of the resistance, a continuously vanishing charge gap as the critical point is approached from the insulating side, and a diverging quasiparticle effective mass from the metallic side. Here, by electrically tuning the effective interaction strength in MoTe2/WSe2 moiré superlattices, we observe a continuous MIT at a fixed filling of one electron per unit cell.
#Spin orbit coupling simulator
Semiconductor moiré materials realize a highly controllable Hubbard model simulator on a triangular lattice9–22, providing a unique opportunity to drive a metal–insulator transition (MIT) via continuous tuning of the electronic interactions. The vicinity of the transition is believed to host exotic states of matter such as quantum spin liquids4–7, exciton condensates8 and unconventional superconductivity1. The evolution of a Landau Fermi liquid into a non-magnetic Mott insulator with increasing electronic interactions is one of the most puzzling quantum phase transitions in physics1–6. Our study paves the way for discovery of emergent phenomena arising from the combined influence of strong correlation and topology in semiconductor moiré materials. Contrary to most known topological phase transitions¹³, it is not accompanied by a bulk charge gap closure. The electric-field-induced topological phase transition from a Mott insulator to a quantum anomalous Hall insulator precedes an insulator-to-metal transition. At half band filling, corresponding to one particle per moiré unit cell, we observe quantized Hall resistance, h/e² (with h and e denoting the Planck’s constant and electron charge, respectively), and vanishing longitudinal resistance at zero magnetic field. Unlike in the AA-stacked heterobilayers¹¹, an out-of-plane electric field not only controls the bandwidth but also the band topology by intertwining moiré bands centred at different layers. Here we report the observation of a quantum anomalous Hall effect in AB-stacked MoTe2 /WSe2 moiré heterobilayers. However, non-trivial band topology has remained unclear. Correlation-driven phenomena, including the Mott insulator2–5, generalized Wigner crystals2,6,9, stripe phases¹⁰ and continuous Mott transition11,12, have been demonstrated. Semiconductor moiré materials provide a highly tuneable platform for studies of electron correlation1–12.
Our theory identifies a new way to achieve topologically nontrivial states in heterobilayer TMD materials.Įlectron correlation and topology are two central threads of modern condensed matter physics. At half filling ν=1, the Coulomb interaction lifts the valley degeneracy and results in a valley-polarized quantum anomalous Hall state, as observed in the experiment.
#Spin orbit coupling full
We show that a time-reversal invariant quantum valley Hall insulator is formed at full filling ν=2, when two moiré bands with opposite Chern numbers are filled. In this Letter, we propose that the pseudomagnetic fields induced by lattice relaxation in moiré MoTe2/WSe2 heterobilayers could naturally give rise to moiré bands with finite Chern numbers. However, how the topologically nontrivial states emerge is not known. Recently, it was reported that both a quantum valley Hall insulating state at filling ν=2 (two holes per moiré unit cell) and a valley-polarized quantum anomalous Hall state at filling ν=1 were observed in AB stacked moiré MoTe2/WSe2 heterobilayers. Nevertheless, the moiré bands in heterobilayer TMDs were believed to be topologically trivial. Moiré 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.
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