Discovery of Dirac nodal loop in non-symmorphic semimetal Nb₃SiTe₆

Ro-Ya Liu^1*, Angus Huang^2,3, Chih-Chuan Su⁴, Raman Sankar⁴, Shih-Chang Weng¹, Meng-Kai Lin⁵, Peng Chen⁶, Joseph Andrew Hlevyack⁵, Alexei Fedorov⁷, Cheng-Maw Cheng¹, Jonathan Denlinger⁷, Chia-Seng Chang⁴, Horng-Tay Jeng⁸, Tien-Ming Chuang⁴, Tai-Chang Chiang⁵

¹NSRRC, Scientific Research Division, Hsinchu City, Taiwan
²Center for quantum technology, National Tsing-Hua University, Hsinchu City, Taiwan
³Dept. of Physics, National Cheng Kung University, Tainan City, Taiwan
⁴Institute of Physics, Academia Sinica, Taipei City, Taiwan
⁵Dept. of Physics, University of Illinois at Urbana-Champaign, Urbana, USA
⁶School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
⁷Advanced light source, Lawrence Berkeley National Lab, Berkeley, USA
⁸Dept. of Physics, National Tsing-Hua University, Hsinchu City, Taiwan

* Presenter:Ro-Ya Liu, email:liu.roya@nsrrc.org.tw

Fermions in hourglass semimetals attract a lot of attention recently. In 3-dimensional
non-symmorphic crystal, the essential band crossing protected by translational
symmetry hosts Dirac nodal loops in a 2-dimensional k-surface. These Dirac nodal
loops at lateral surfaces are the origin of many unusual properties in transport or
optical response, such as anisotropic electron transport, and chiral anomaly. We report
herein a detailed study of a non-symmorphic crystal, Nb 3 SiTe 6 by using angle-
resolved photoemission spectroscopy. Band dispersion along XS is mapped out by
varying photon energies. The crossing point (Dirac point) of a Dirac cone gradually
shifts to higher binding energy with the change of k z from X to S point. The energy
shift provides straightforward evidence for Dirac nodal loop.

Keywords: Hourglass semimetal, Dirac nodal loop, Angle-resolved photoemission spectroscopy