Topological nodal-line fermions in spin-orbit metal PbTaSe2.
Topological nodal-line fermions in spin-orbit metal PbTaSe2.
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DOI：
10.1038/ncomms10556
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发表时间：
2016-02-02
影响因子：
16.6
通讯作者：
Hasan MZ
中科院分区：
文献类型：
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作者：
Bian G;Chang TR;Sankar R;Xu SY;Zheng H;Neupert T;Chiu CK;Huang SM;Chang G;Belopolski I;Sanchez DS;Neupane M;Alidoust N;Liu C;Wang B;Lee CC;Jeng HT;Zhang C;Yuan Z;Jia S;Bansil A;Chou F;Lin H;Hasan MZ
拓扑半金属可以支持动量空间中的一维费米线或零维外尔点，其中价带和导带接触。虽然外尔半金属的简并点对任何保持平移对称性的扰动都是鲁棒的，但节线需要额外的晶体对称性（如镜面反射）的保护。在这里，我们报告，基于系统的理论研究和详细的实验表征，存在的拓扑线态的非中心对称化合物PbTaSe 2与强自旋轨道耦合。值得注意的是，PbTaSe 2中的自旋轨道节线不仅受到反射对称性的保护，而且还具有整数拓扑不变量的特征。我们详细的角分辨光电子能谱测量、第一性原理模拟和理论拓扑分析首次阐明了拓扑线费米子态和相关表面态形成的物理机制，从而为探索凝聚态系统中拓扑线费米子的奇异性质铺平了道路。 费米能级附近出现的节线形能带在拓扑物质中具有独特的性质，这一点尚未在真实的材料中得到证实。在这里，作者报告了在非中心对称单晶自旋轨道半金属PbTaSe 2中存在拓扑线态。
Topological 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. Nodal-line shaped bands appearing near the Fermi level host unique properties in topological matter, which has yet to be confirmed in real materials. Here, the authors report the existence of topological nodal-line states in the non-centrosymmetric single-crystalline spin-orbit semimetal PbTaSe2.