Topological nodal-line fermions in spin-orbit metal PbTaSe2

• DOI: 10.1038/ncomms10556
• Publication Date: 2016-02-02T10:52:27Z
• Authors: Guang Bian; Tay-Rong Chang; Raman Sankar; Su-Yang Xu; Hao Zheng; Titus Neupert; Ching-Kai Chiu; Shin-Ming Huang; Guoqing Chang; Ilya Belopolski; Daniel S. Sanchez; Madhab Neupane; Nasser Alidoust; Chang Liu; BaoKai Wang; Chi-Cheng Lee; Horng-Tay Jeng; Chenglong Zhang; Zhujun Yuan; Shuang Jia; Arun Bansil; Fangcheng Chou; Hsin Lin; M. Zahid Hasan
• Keywords: fermion; theoretical model; Science; Q; 500; momentum; surface area; theoretical study; 530; 01 natural sciences; experimental study; Article; 0103 physical sciences; numerical model; symmetry

AbstractTopological semimetals can support one-dimensional Fermi lines or zero-dimensional Weyl points 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. Here we report, based on a systematic theoretical study and a detailed experimental characterization, the existence of topological nodal-line states in the non-centrosymmetric compound PbTaSe2 with strong spin-orbit coupling. 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 detailed angle-resolved photoemission measurements, first-principles simulations and theoretical topological analysis illustrate the physical mechanism underlying the formation of the topological nodal-line states and associated surface states for the first time, thus paving the way towards exploring the exotic properties of the topological nodal-line fermions in condensed matter systems.