Crystal Field Effect Induced Topological Crystalline Insulators In Monolayer IV–VI Semiconductors,Nano Letters

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Crystal Field Effect Induced Topological Crystalline Insulators In Monolayer IV–VI Semiconductors
Nano Letters ( IF 9.6 ) Pub Date : 2015-03-09 00:00:00 , DOI: 10.1021/acs.nanolett.5b00308
Junwei Liu ₁ , Xiaofeng Qian ₂ , Liang Fu ₁

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Two-dimensional (2D) topological crystalline insulators (TCIs) were recently predicted in thin films of the SnTe class of IV–VI semiconductors, which can host metallic edge states protected by mirror symmetry. As thickness decreases, quantum confinement effect will increase and surpass the inverted gap below a critical thickness, turning TCIs into normal insulators. Surprisingly, based on first-principles calculations, here we demonstrate that (001) monolayers of rocksalt IV–VI semiconductors XY (X = Ge, Sn, Pb and Y = S, Se, Te) are 2D TCIs with the fundamental band gap as large as 260 meV in monolayer PbTe. This unexpected nontrivial topological phase stems from the strong crystal field effect in the monolayer, which lifts the degeneracy between p_x,y and p_z orbitals and leads to band inversion between cation p_z and anion p_x,y orbitals. This crystal field effect induced topological phase offers a new strategy to find and design other atomically thin 2D topological materials.

中文翻译：

晶体场效应诱导的单层IV–VI半导体拓扑晶体绝缘子

最近在IV-VI半导体的SnTe类薄膜中预测了二维（2D）拓扑晶体绝缘体（TCI），该薄膜可以容纳受到镜面对称性保护的金属边缘态。随着厚度的减小，量子限制效应将增加并超过临界厚度以下的倒置间隙，从而将TCI变成普通的绝缘体。出乎意料的是，基于第一性原理的计算，我们证明了（001）岩盐IV-VI半导体XY（X = Ge，Sn，Pb和Y = S，Se，Te）的单层是2D TCI，其基带隙为在单层PbTe中最大为260 meV。这种出乎意料的非平凡的拓扑相源于单层中的强晶场效应，从而提升了p _x，y和p _z之间的简并性并导致阳离子p _z和阴离子p _x，y轨道之间的能带反转。这种由晶体场效应引起的拓扑相为寻找和设计其他原子薄的2D拓扑材料提供了新的策略。

更新日期：2015-03-09

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