Abstract：Topological semimetals are a new type of matter with one-dimensional Fermi lines or zero-dimensional Weyl or Dirac points in momentum space. Here using first-principles calculations, we find that the non-centrosymmetric PbTaS$_2$ is a topological nodal line semimetal. In the absence of spin-orbit coupling (SOC), one band inversion happens around a high symmetrical $H$ point, which leads to forming a nodal line. The nodal line is robust and protected against gap opening by mirror reflection symmetry even with the inclusion of strong SOC. In addition, it also hosts exotic drumhead surface states either inside or outside the projected nodal ring depending on surface termination. The robust bulk nodal lines and drumhead-like surface states with SOC in PbTaS$_2$ make it a potential candidate material for exploring the freakish properties of the topological nodal line fermions in condensed matter systems.
Chen Y L, Analytis J G, Chu J H, Liu Z K, Mo S K, Qi X L, Zhang H J, Lu D H, Dai X, Fang Z, Zhang S C, Fisher I R, Hussain Z and Shen Z X 2009 Science325 178
Huang S M, Xu S Y, Belopolski I, Lee C C, Chang G, Wang B, Alidoust N, Bian G, Neupane M, Zhang C, Jia S, Bansil A, Lin H and Hasan M Z 2015 Nat. Commun.6 7373
[12]
Xu S Y, Belopolski I, Alidoust N, Neupane M, Bian G, Zhang C, Sankar R, Chang G, Yuan Z, Lee C C, Huang S M, Zheng H, Ma J, Sanchez D S, Wang B, Bansil A, Chou F, Shibayev P P, Lin H, Jia S and Hasan M Z 2015 Science349 613
Bian G, Chang T R, Sankar R, Xu S Y, Zheng H, Neupert T, Chiu C K, Huang S M, Chang G, Belopolski I, Sanchez D S, Neupane M, Alidoust N, Liu C, Wang B, Lee C C, Jeng H T, Zhang C, Yuan Z, Jia S, Bansil A, Chou F, Lin H and Hasan M Z 2016 Nat. Commun.7 10556
[22]
Bian G, Chang T R, Zheng H, Velury S, Xu S Y, Neupert T, Chiu C K, Huang S M, Sanchez D S, Belopolski I, Alidoust N, Chen P J, Chang G, Bansil A, Jeng H T, Lin H and Hasan M Z 2016 Phys. Rev. B 93 121113
2017, Vol. 34 
