Observation of the topological surface state in the nonsymmorphic topological insulator KHgSb

A. J. Liang, J. Jiang, M. X. Wang, Y. Sun, N. Kumar, C. Shekhar, C. Chen, H. Peng, C. W. Wang, X. Xu, H. F. Yang, S. T. Cui, G. H. Hong, Y.-Y. Xia, S.-K. Mo, Q. Gao, X. J. Zhou, L. X. Yang, C. Felser, B. H. Yan, Z. K. Liu, and Y. L. Chen
Phys. Rev. B 96, 165143 – Published 25 October 2017
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Abstract

Topological insulators represent unusual topological quantum states, typically with gapped bulk band structure but gapless surface Dirac fermions protected by time-reversal symmetry. Recently, a distinct kind of topological insulator resulting from nonsymmorphic crystalline symmetry was proposed in the KHgX (X=As, Sb, Bi) compounds. Unlike regular topological crystalline insulators, the nonsymmorphic glide-reflection symmetry in KHgX guarantees the appearance of an exotic surface fermion with hourglass shape dispersion (where two pairs of branches switch their partners) residing on its (010) side surface, contrasting to the usual two-dimensional Dirac fermion form. Here, by using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structures of KHgSb on both (001) and (010) surfaces and reveal the unique in-gap surface states on the (010) surface with delicate dispersion consistent with the “hourglass Fermion” recently proposed. Our experiment strongly supports that KHgSb is a nonsymmorphic topological crystalline insulator with hourglass fermions, which serves as an important step to the discovery of unique topological quantum materials and exotic fermions protected by nonsymmorphic crystalline symmetry.

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  • Received 1 June 2017

DOI:https://doi.org/10.1103/PhysRevB.96.165143

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

A. J. Liang1, J. Jiang1,2,3, M. X. Wang1, Y. Sun4, N. Kumar4, C. Shekhar4, C. Chen5, H. Peng5, C. W. Wang6, X. Xu2,7, H. F. Yang1,6, S. T. Cui1, G. H. Hong1, Y.-Y. Xia1,4, S.-K. Mo2, Q. Gao8, X. J. Zhou8,9, L. X. Yang7, C. Felser4, B. H. Yan10, Z. K. Liu1,*, and Y. L. Chen1,5,7,11,†

  • 1School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, People's Republic of China
  • 2Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
  • 3Pohang Accelerator Laboratory, POSTECH, Pohang 790-784, Korea
  • 4Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
  • 5Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
  • 6State Key Laboratory of Functional Materials for Informatics, SIMIT, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China
  • 7State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics and Collaborative Innovation Center of Quantum Matter, Tsinghua University, Beijing 100084, People's Republic of China
  • 8Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
  • 9Collaborative Innovation Center of Quantum Matter, Beijing 100190, People's Republic of China
  • 10Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
  • 11Hefei Science Center, CAS and SCGY, University of Science and Technology of China, Hefei 230026, People's Republic of China

  • *liuzhk@shanghaitech.edu.cn
  • yulin.chen@physics.ox.ac.uk

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Issue

Vol. 96, Iss. 16 — 15 October 2017

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