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. In a magnetic topological insulator, nontrivial band topology combines with magnetic order to produce exotic states of matter, such as quantum anomalous Hall (QAH) insulators and axion insulators. In this work, we probe quantum transport in MnBi2Te4 thin flakes—a topological insulator with intrinsic magnetic order. In this layered van der Waals crystal, the ferromagnetic layers couple antiparallel to each other; atomically thin MnBi2Te4, however, becomes ferromagnetic when the sample has an odd number of septuple layers. We observe a zero-field QAH effect in a five–septuple-layer specimen at 1.4 kelvin, and an external magnetic field further raises the quantization temperature to 6.5 kelvin by aligning all layers ferromagnetically. The results establish MnBi2Te4 as an ideal arena for further exploring various topological phenomena with a spontaneously broken time-reversal symmetry.

中文翻译：

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本征磁拓扑绝缘体MnBi2Te4中的量子反常霍尔效应

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。在磁拓扑绝缘体中，非平凡带拓扑与磁序相结合以产生奇异的物质状态，例如量子反常霍尔 (QAH) 绝缘体和轴子绝缘体。在这项工作中，我们探测了 MnBi2Te4 薄片（一种具有内在磁序的拓扑绝缘体）中的量子传输。在这种分层的范德瓦尔斯晶体中，铁磁层彼此反平行；然而，当样品具有奇数个七层时，原子级薄的 MnBi2Te4 变成铁磁性的。我们在 1.4 开尔文的五七层样品中观察到零场 QAH 效应，外部磁场通过铁磁对齐所有层进一步将量化温度提高到 6.5 开尔文。