Quantum anomalous Hall goes intrinsic Quantum anomalous Hall effect—the appearance of quantized Hall conductance at zero magnetic field—has been observed in thin films of the topological insulator Bi2Se3 doped with magnetic atoms. The doping, however, introduces inhomogeneity, reducing the temperature at which the effect occurs. Two groups have now observed quantum anomalous Hall effect in intrinsically magnetic materials (see the Perspective by Wakefield and Checkelsky). Serlin et al. did so in twisted bilayer graphene aligned to hexagonal boron nitride, where the effect enabled the switching of magnetization with tiny currents. In a complementary work, Deng et al. observed quantum anomalous Hall effect in the antiferromagnetic layered topological insulator MnBi2Te4. Science, this issue p. 900, p. 895; see also p. 848 Transport measurements indicate quantized Hall conductance without a magnetic field. The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern number C = 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampere controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.

中文翻译：

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莫尔异质结构中的内在量子化异常霍尔效应

量子反常霍尔进入本征量子反常霍尔效应——在零磁场下量子化霍尔电导的出现——已在掺杂有磁性原子的拓扑绝缘体 Bi2Se3 的薄膜中观察到。然而，掺杂引入了不均匀性，降低了效应发生的温度。现在有两个小组在固有磁性材料中观察到了量子反常霍尔效应（参见 Wakefield 和 Checkelsky 的观点）。塞林等人。在与六方氮化硼对齐的扭曲双层石墨烯中做到了这一点，其中这种效应能够用微小的电流切换磁化。在补充工作中，邓等人。在反铁磁层状拓扑绝缘体 MnBi2Te4 中观察到量子反常霍尔效应。科学，这个问题 p。900，第。895; 另见第。848 传输测量表明没有磁场的量化霍尔电导。量子反常霍尔 (QAH) 效应结合了拓扑和磁性，可在零磁场下产生精确量化的霍尔电阻。我们报告了在与六方氮化硼对齐的扭曲双层石墨烯中观察到 QAH 效应。这种效应是由内在的强相互作用驱动的，它将电子极化成一个单一的自旋和谷分辨莫尔条纹，陈数 C = 1。与磁性掺杂系统相比，测量的传输能隙大于居里温度在零磁场下，磁序和量化到 von Klitzing 常数的 0.1% 以内持续到几个开尔文的温度。