Two-Dimensional Node-Line Semimetals in a Honeycomb-Kagome Lattice  

作　　者：卢金炼 罗伟 李雪阳 杨晟祺 曹觉先 龚新高 向红军 

机构地区：[1]Department of Physics, Xiangtan University, Xiangtan 411105 [2]Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433 [3]Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093

出　　处：《Chinese Physics Letters》2017年第5期106-110,共5页中国物理快报（英文版）

基　　金：Supported by the National Natural Science Foundation of China under Grant No 11374056;the Special Funds for Major State Basic Research under Grant No 2015CB921700;the Program for Professor of Special Appointment(Eastern Scholar);the Qing Nian Ba Jian Program,and the Fok Ying Tung Education Foundation

摘　　要：Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional （3D） Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals （NLSs）. In particular, several compounds （e.g., certain 3D graphene networks, Cu3PdN, Ca3P2 ） were discovered to be 3D NLSs, in which the conduction and valence bands cross at closed lines in the Brillouin zone. Except for the two-dimensional （2D） Dirac semimetal （e.g., graphene）, 2D topological semimetals are much less investigated. Here we propose a new concept of a 2D NLS and suggest that this state could be realized in a new mixed lattice （named as HK lattice） composed by Kagome and honeycomb lattices. It is found that A3B2 （A is a group-liB cation and B is a group-VA anion） compounds （such as Hg3As2） with the HK lattice are 2D NLSs due to the band inversion between the cation Hg-s orbital and the anion As-pz orbital with respect to the mirror symmetry. Since the band inversion occurs between two bands with the same parity, this peculiar 2D NLS could be used as transparent conductors. In the presence of buckling or spin-orbit coupling, the 2D NLS state may turn into a 2D Dirac semimetal state or a 2D topological crystalline insulating state. Since the band gap opening due to buckling or spin-orbit coupling is small, Hg3As3 with the HK lattice can still be regarded as a 2D NLS at room temperature. Our work suggests a new route to design topological materials without involving states with opposite parities.Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional （3D） Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals （NLSs）. In particular, several compounds （e.g., certain 3D graphene networks, Cu3PdN, Ca3P2 ） were discovered to be 3D NLSs, in which the conduction and valence bands cross at closed lines in the Brillouin zone. Except for the two-dimensional （2D） Dirac semimetal （e.g., graphene）, 2D topological semimetals are much less investigated. Here we propose a new concept of a 2D NLS and suggest that this state could be realized in a new mixed lattice （named as HK lattice） composed by Kagome and honeycomb lattices. It is found that A3B2 （A is a group-liB cation and B is a group-VA anion） compounds （such as Hg3As2） with the HK lattice are 2D NLSs due to the band inversion between the cation Hg-s orbital and the anion As-pz orbital with respect to the mirror symmetry. Since the band inversion occurs between two bands with the same parity, this peculiar 2D NLS could be used as transparent conductors. In the presence of buckling or spin-orbit coupling, the 2D NLS state may turn into a 2D Dirac semimetal state or a 2D topological crystalline insulating state. Since the band gap opening due to buckling or spin-orbit coupling is small, Hg3As3 with the HK lattice can still be regarded as a 2D NLS at room temperature. Our work suggests a new route to design topological materials without involving states with opposite parities.

关 键 词：As HG NLS Two-Dimensional Node-Line Semimetals in a Honeycomb-Kagome Lattice 

分 类 号：O76[理学—晶体学]