Experimental evidence of hourglass fermion in the candidate nonsymmorphic topological insulator KHgSb

Junzhang Ma; Changjiang Yi; Baiqing Lv; ZhiJun Wang; Simin Nie; Le Wang; Lingyuan Kong; Yaobo Huang; Pierre Richard; Peng Zhang; Koichiro Yaji; Kenta Kuroda; Shik Shin; Hongming Weng; Bogdan Andrei Bernevig; Youguo Shi; Tian Qian; Hong Ding

doi:10.1126/sciadv.1602415

Experimental evidence of hourglass fermion in the candidate nonsymmorphic topological insulator KHgSb

Sci Adv. 2017 May 5;3(5):e1602415. doi: 10.1126/sciadv.1602415. eCollection 2017 May.

Authors

Junzhang Ma¹, Changjiang Yi¹, Baiqing Lv¹, ZhiJun Wang², Simin Nie¹, Le Wang¹, Lingyuan Kong¹, Yaobo Huang³, Pierre Richard^{1

4

5}, Peng Zhang⁶, Koichiro Yaji⁶, Kenta Kuroda⁶, Shik Shin⁶, Hongming Weng^{1

4}, Bogdan Andrei Bernevig², Youguo Shi¹, Tian Qian^{1

4}, Hong Ding^{1

4

5}

Affiliations

¹ Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
² Department of Physics, Princeton University, Princeton, NJ 08544, USA.
³ Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
⁴ Collaborative Innovation Center of Quantum Matter, Beijing, China.
⁵ School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China.
⁶ Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.

Abstract

Topological insulators (TIs) host novel states of quantum matter characterized by nontrivial conducting boundary states connecting valence and conduction bulk bands. All TIs discovered experimentally so far rely on either time-reversal or mirror crystal symmorphic symmetry to protect massless Dirac-like boundary states. Several materials were recently proposed to be TIs with nonsymmorphic symmetry, where a glide mirror protects exotic surface fermions with hourglass-shaped dispersion. However, an experimental confirmation of this new fermion is missing. Using angle-resolved photoemission spectroscopy, we provide experimental evidence of hourglass fermions on the (010) surface of crystalline KHgSb, whereas the (001) surface has no boundary state, in agreement with first-principles calculations. Our study will stimulate further research activities of topological properties of nonsymmorphic materials.

Keywords: Hourglass fermion; nonsymmorphic materials; topological insulator.