Valley-coherent quantum anomalous Hall state in AB-stacked MoTe2/WSe2 bilayers

Kavli Affiliate: Jie Shan

| First 5 Authors: Zui Tao, Bowen Shen, Shengwei Jiang, Tingxin Li, Lizhong Li

| Summary:

Moir’e materials provide fertile ground for the correlated and topological
quantum phenomena. Among them, the quantum anomalous Hall (QAH) effect, in
which the Hall resistance is quantized even under zero magnetic field, is a
direct manifestation of the intrinsic topological properties of a material and
an appealing attribute for low-power electronics applications. The QAH effect
has been observed in both graphene and transition metal dichalcogenide (TMD)
moir’e materials. It is thought to arise from the interaction-driven valley
polarization of the narrow moir’e bands. Here, we show surprisingly that the
newly discovered QAH state in AB-stacked MoTe2/WSe2 moir’e bilayers is not
valley-polarized but valley-coherent. The layer- and helicity-resolved optical
spectroscopy measurement reveals that the QAH ground state possesses
spontaneous spin (valley) polarization aligned (anti-aligned) in two TMD
layers. In addition, saturation of the out-of-plane spin polarization in both
layers occurs only under high magnetic fields, supporting a canted spin
texture. Our results call for a new mechanism for the QAH effect and highlight
the potential of TMD moir’e materials with strong electronic correlations and
spin-orbit interactions for exotic topological states.

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