论文标题
量子异常的霍尔效应和电场诱导的拓扑相过渡，以ab堆放的MOTE $ {} _ 2 $/WSE $ {} _ 2 $Moiréheterobilayers
Quantum anomalous Hall effect and electric-field-induced topological phase transition in AB-stacked MoTe${}_2$/WSe${}_2$ moiré heterobilayers
论文作者
论文摘要
我们提出了一种新的机制，以解释量子异常的效果（QAH）效应和电场诱导的拓扑相过渡，以AB堆叠的MOTE $ {} _ 2 $/WSE $ {} _ 2 $MoiréHeterobilayers$ n = 1 $ hole填充。我们建议QAH状态的Chern带是由由最高的两个Moiré孔带组成的固有带反转产生的，该孔带具有相反的山谷数量和一个由两个Coulomb-Interaction驱动的磁性顺序引起的间隙开口。这些磁性顺序，包括平面$ 120^{\ Circ} $ - Néel订单和平面内磁性顺序，通过相应的平面交换场与Moiré带相互作用。 Néel秩序确保了绝缘差距，铁磁顺序诱导了非零的Chern数，并且这两个顺序均导致时间反转对称性破裂。 néel顺序是从Hartree-Fock交换相互作用中获取的，铁磁性顺序的形成归因于层间式凝结和激子铁磁性。激子铁磁剂可以通过激发式玻色 - 哈伯物理学和berezinskii-kosterlitz-bereless-thouless跃迁来证明。在低电场中，平衡状态是mott-usulator态。在某个电场上，由孔占用带组成的相关绝缘状态，激子冷凝物变成了一个新的热力学稳定相，并且随着铁磁阶的出现，拓扑相过渡发生。讨论了当前理论与实验观察之间的一致性。该机制解释了实验观察，包括QAH状态的自旋偏振/谷化性质，拓扑相变的缺乏电荷差距闭合，倾斜的自旋纹理和绝缘体到金属转变。
We propose a new mechanism to explain the quantum anomalous Hall (QAH) effect and the electric-field-induced topological phase transition in AB-stacked MoTe${}_2$/WSe${}_2$ moiré heterobilayers at $ν=1$ hole filling. We suggest that the Chern band of the QAH state is generated from an intrinsic band inversion composed of the highest two moiré hole bands with opposite valley numbers and a gap opening induced by two Coulomb-interaction-driven magnetic orders. These magnetic orders, including an in-plane $120^{\circ}$-Néel order and an in-plane ferromagnetic order, interact with moiré bands via corresponding in-plane exchange fields. The Néel order ensures the insulating gap, the ferromagnetic order induces the non-zero Chern number, and both orders contribute to time-reversal symmetry breaking. The Néel order is acquired from the Hartree-Fock exchange interaction, and the formation of ferromagnetic order is attributed to interlayer-exciton condensation and exciton ferromagnetism. The exciton ferromagnetism can be demonstrated by excitonic Bose-Hubbard physics and Berezinskii-Kosterlitz-Thouless transition. In low electric fields, the equilibrium state is a Mott-insulator state. At a certain electric field, a correlated insulating state composed of the hole-occupied band and the exciton condensate becomes a new thermodynamically stable phase, and the topological phase transition occurs as the ferromagnetic order emerges. The consistency between the present theory and experimental observations is discussed. Experimental observations, including the spin-polarized/valley-coherent nature of the QAH state, the absence of charge gap closure at the topological phase transition, the canted spin texture, and the insulator-to-metal transition, are interpreted by the mechanism.
