Observation of non-trivial topological electronic structure of orthorhombic SnSe
H. J. Zheng, W. J. Shi, C. W. Wang, Y. Y. Lv, W. Xia, B. H. Li, F. Wu, S. M. He, K. Huang, S. T. Cui, C. Chen, H. F. Yang, A. J. Liang, M. X. Wang, Z. Sun, S. H… 展开作者
H. J. Zheng, W. J. Shi, C. W. Wang, Y. Y. Lv, W. Xia, B. H. Li, F. Wu, S. M. He, K. Huang, S. T. Cui, C. Chen, H. F. Yang, A. J. Liang, M. X. Wang, Z. Sun, S. H. Yao, Y. B. Chen, Y. F. Guo, Q. X. Mi, L. X. Yang, M. S. Bahramy, Z. K. Liu, Y. L. Chen
备注：
17 pages, 4 figures, accepted for publication in Physical Review Materials
Topological electronic structures are key to the topological classification of quantum materials and play an important role in their physical properties and applications. Recently, SnSe has attracted great research interests due to its superior thermoelectric performance. However, it's topological nature has long been ignored. In this work, by combining synchrotron-based angle-resolved photoemission spectroscopy and ab-initio calculations, we systematically investigated the topological electronic structure of orthorhombic SnSe. By identifying the continuous gap in the valence bands due to the band inversion and the topological surface states on its (001) surface, we establish SnSe as a strong topological insulator. Furthermore, we studied the evolution of the topological electronic structure and propose the topological phase diagram in SnSe1-xTex. Our work reveals the topological non-trivial nature of SnSe and provides new understandings of its intriguing transport properties.
Rock-salt SnS and SnSe: Native Topological Crystalline Insulators
与时间反演拓扑绝缘体不同，最近发现的拓扑晶体绝缘体（TCI）中具有狄拉克锥色散的表面金属态受到晶体对称性的保护。到目前为止，已经在SnTe和相关合金Pb $_{1-x}$ Sn $_{x}$ Se/Te中观察到TCI行为，其包含具有大自旋轨道耦合（SOC）的重元素。在这里，通过结合第一性原理和{ \it ab initio}紧束缚计算，我们报告的TCI在相对较轻的岩盐SnS和SnSe的形成。该TCI的特征在于在高对称性（001）、（110）和（111）表面处的偶数个狄拉克锥，这些表面受到关于（$\bar{1}$ 10）镜面的反射对称性的保护。我们发现SnS和SnSe都具有本征反转的能带结构，并且SOC仅是打开体带隙所必需的。体积膨胀后的体带隙演化揭示了从环境压力TCI到拓扑平凡绝缘体的拓扑转变。我们的研究结果表明，SOC单独是不足以驱动的拓扑结构的转变。
Engineering topological flat bands in $Γ$-valley moiré systems with Ising-type SOC: twisted 1T-ZrS$_2$ and 1T-SnSe$_2$
Donostia International Physics Center (DIPC)（多诺西亚国际物理中心）；Department of Physics, University of Texas at Dallas（德克萨斯大学达拉斯分校物理系）；Princeton Center for Theoretical Science, Princeton University（普林斯顿大学理论科学中心）；Department of Physics, Princeton University（普林斯顿大学物理系）；Department of Physics, University of Science and Technology of China（中国科学技术大学物理系）；Rudolf Peierls Centre for Theoretical Physics, University of Oxford（牛津大学鲁道夫·派尔斯理论物理中心）；School of Applied and Engineering Physics, Cornell University（康奈尔大学应用与工程物理学院）；Department of Physics, Cornell University（康奈尔大学物理系）；Kavli Institute at Cornell for Nanoscale Science（康奈尔纳米科学卡弗里研究所）；Max Planck Institute for the Structure and Dynamics of Matter（马克斯·普朗克物质结构与动力学研究所）
Temperature-Driven Topological Transition in 1T'-MoTe2
Weyl半金属的拓扑结构要求存在唯一的表面态。表面状态已经在光谱测量中可视化，但它们与材料拓扑特征的联系在很大程度上尚未探索。1 T '-MoTe 2，提供了一个独特的机会来研究这种联系。这种材料在240 K时经历了一个相变，将结构从斜方晶系（假定的外尔半金属）变为单斜晶系（平凡金属），同时在很大程度上保持了其体电子结构。在这里，我们表明，从依赖于温度的准粒子干涉测量，这种结构转变也作为一个拓扑开关的表面状态在1 T '-MoTe 2。在低温下，我们观察到强烈的准粒子散射，在这种材料的表面态的理论预测和光电发射测量相一致。相比之下，在室温下进行的测量显示完全没有与平凡的表面状态相关联的散射波矢量。这些不同的准粒子散射行为表明，1 T '-MoTe 2是理想的分离拓扑和平凡的电子现象，通过温度依赖的测量。
