Prediction and observation of an antiferromagnetic topological insulator
Prediction and observation of an antiferromagnetic topological insulator
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DOI：
10.1038/s41586-019-1840-9
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发表时间：
2019-12-19
期刊：
影响因子：
64.8
通讯作者：
Chulkov, E. V.
中科院分区：
文献类型：
--
作者：
Otrokov, M. M.;Klimovskikh, I. I.;Chulkov, E. V.
磁性拓扑绝缘体是一种窄禁带半导体材料，它结合了联合收割机的非平凡能带拓扑和磁序（1）。与磁性拓扑绝缘体不同的是，磁性拓扑绝缘体的某些表面可能存在间隙，这使得许多在自旋电子学中具有潜在应用的奇异现象成为可能（1），例如量子反常霍尔效应（2）和手性马约拉纳费米子（3）。到目前为止，磁性拓扑绝缘体只能通过用3d过渡金属元素掺杂非磁性拓扑绝缘体来制造;然而，这种方法导致这些材料的磁性（4）和电子（5）非常不均匀，限制了对非常低的温度（2，3）的重要影响的观察。一种内禀磁性拓扑绝缘体--一种化学计量有序的磁性化合物--可能是这些问题的理想解决方案，但到目前为止还没有观察到这样的材料。在这里，我们预测从头计算，并进一步确认使用各种实验技术的实现反铁磁拓扑绝缘体的层状货车德瓦尔斯化合物MnBi 2 Te 4。MnBi 2 Te 4的反铁磁有序性使得它在时间反演和连续晶格平移对称性的组合下保持不变，从而产生Z（2）拓扑分类; MnBi 2 Te 4的Z（2）= 1，证实了它的拓扑非平凡性质。实验结果表明，MnBi_2Te_4的（0001）面在拓扑表面态下具有较大的带隙.我们期望这一特性最终能够观察到许多基本现象，其中包括量子化磁电耦合（6-8）和轴子电动力学（9，10）。其他奇异现象可以在比目前达到的温度高得多的温度下实现，例如量子反常霍尔效应（2）和手性马约拉纳费米子（3）。
Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order(1). Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics(1), such as the quantum anomalous Hall effect(2) and chiral Majorana fermions(3). So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic(4) and electronic(5) properties of these materials, restricting the observation of important effects to very low temperatures(2,3). An intrinsic magnetic topological insulator-a stoichiometric well ordered magnetic compound-could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBi2Te4. The antiferromagnetic ordering that MnBi2Te4 shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a Z(2) topological classification; Z(2) = 1 for MnBi2Te4, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi2Te4 exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling(6-8) and axion electrodynamics(9,10). Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect(2) and chiral Majorana fermions(3).