Topological Nodal-Line Fermions in Strong Spin-Orbit Metal PbTaSe₂
Guang Bian1, Tay-Rong Chang2,1*, Raman Sankar3, Su-Yang Xu1, Hao Zheng1, Titus Neupert1,4, Ching-Kai Chiu5, Shin-Ming Huang6,7, Guoqing Chang6,7, Ilya Belopolski1, Daniel S. Sanchez1, Madhab Neupane1, Nasser Alidoust1, Chang Liu1, BaoKai Wang6,7,8, Chi-Cheng Lee6,7, Horng-Tay Jeng2,9, Chenglong Zhang10, Zhujun Yuan10, Shuang Jia10, Arun Bansil8, Fangcheng Chou3, Hsin Lin6,7, M. Zahid Hasan1,11
1Joseph Henry Laboratory, Department of Physics, Princeton University, New Jersey, USA
2Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
3Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
4Princeton Center for Theoretical Science, Princeton University, New Jersey, USA
5Department of Physics and Astronomy, University of British Columbia, BC, Canada
6Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore
7Department of Physics, National University of Singapore, Singapore, Singapore
8Department of Physics, Northeastern University, Boston,Massachusetts, USA
9Institute of Physics, Academia Sinica, Taipei, Taiwan
10ICQM, School of Physics, Peking University, Beijing, China
11Princeton Center for Complex Materials, Princeton University, New Jersey, USA
* presenting author:Tay-Rong Chang,
In a typical three-dimensional metal, the low-energy excitations are found on a two-dimensional closed Fermi surface in momentum space. Topological semimetals, by contrast, can support one-dimensional Fermi lines or zero-dimensional Fermi-Weyl points, at locations in momentum space, where the valence and conduction bands touch. While the degeneracy points in Weyl semimetals are robust against any perturbation that preserves translational symmetry, nodal lines require protection by additional crystalline symmetries such as mirror reflection. In this talk, I will demonstrate the prediction of topological nodal-line states in the non-centrosymmetric compound single-crystalline PbTaSe₂ with strong spin-orbit coupling based on the first-principles electronic structure calculations. Remarkably, the spin-orbit nodal lines in PbTaSe₂ are not only protected by the reflection symmetry but also characterized by an integer topological invariant. Our theoretical analysis illustrate the physical mechanism underlying the formation of the topological nodal-line states and associated surface states. The calculated surface states are in good agreement with angle-resolved photoemission (ARPES) measurements [1].

[1] arXiv:1505.03069, G. Bian, T.-R. Chang, R. Sankar, et al.

Keywords: first-principles calculations, topological insulator, spin-orbit coupling, Nodal line, PbTaSe2