Zhang Rui-Xing, Wu Fengcheng, Das Sarma S
Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
Phys Rev Lett. 2020 Apr 3;124(13):136407. doi: 10.1103/PhysRevLett.124.136407.
We propose MnBi_{2n}Te_{3n+1} as a magnetically tunable platform for realizing various symmetry-protected higher-order topology. Its canted antiferromagnetic phase can host exotic topological surface states with a Möbius twist that are protected by nonsymmorphic symmetry. Moreover, opposite surfaces hosting Möbius fermions are connected by one-dimensional chiral hinge modes, which offers the first material candidate of a higher-order topological Möbius insulator. We uncover a general mechanism to feasibly induce this exotic physics by applying a small in-plane magnetic field to the antiferromagnetic topological insulating phase of MnBi_{2n}Te_{3n+1}, as well as other proposed axion insulators. For other magnetic configurations, two classes of inversion-protected higher-order topological phases are ubiquitous in this system, which both manifest gapped surfaces and gapless chiral hinge modes. We systematically discuss their classification, microscopic mechanisms, and experimental signatures. Remarkably, the magnetic-field-induced transition between distinct chiral hinge mode configurations provides an effective "topological magnetic switch".
我们提出MnBi₂ₙTe₃ₙ₊₁作为一个磁可调平台，用于实现各种对称性保护的高阶拓扑结构。其倾斜反铁磁相可以承载具有莫比乌斯扭曲的奇异拓扑表面态，这些表面态由非对称空间群对称性保护。此外，承载莫比乌斯费米子的相对表面通过一维手性铰链模式相连，这为高阶拓扑莫比乌斯绝缘体提供了首个材料候选者。我们揭示了一种通用机制，通过对MnBi₂ₙTe₃ₙ₊₁以及其他提出的轴子绝缘体的反铁磁拓扑绝缘相施加一个小的面内磁场，来切实诱导这种奇异物理现象。对于其他磁构型，两类由空间反演对称性保护的高阶拓扑相在该系统中普遍存在，它们都表现出有能隙的表面和无能隙的手性铰链模式。我们系统地讨论了它们的分类、微观机制和实验特征。值得注意的是，不同手性铰链模式构型之间的磁场诱导转变提供了一个有效的“拓扑磁开关”。
