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arXiv 1603.04596cond-mat.mtrl-sci
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二维蜂窝-Kagome格点中的结点线半金属

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

J. L. Lu, W. Luo, X. Y. Li, S. Q. Yang, J. X. Cao, X. G. Gong, H. J. Xiang

摘要:

最近,拓扑绝缘体的概念已被推广到拓扑半金属,包括三维(3D)Weyl半金属,3D Dirac半金属,和3D节点线半金属。特别地,几种化合物(例如,某些三维石墨烯网络(Cu 3 PdN、Ca 3 P2)被发现是3D节点线半金属,其中导带和价带在布里渊区的闭合线处交叉。除了二维(2D)狄拉克半金属(例如,在石墨烯中),2D拓扑半金属的研究要少得多。在这里,我们提出了一个新的概念,二维节点线半金属,并建议这种状态可以实现在一个新的混合晶格(我们称之为HK晶格)由kagome和蜂窝晶格。我们发现,由于阳离子s轨道和阴离子pz轨道之间的能带反转,具有HK晶格的A_3B_2(A为IIB族阳离子,B为VA族阴离子)化合物(如Hg_3As_2)是二维节线半金属.当存在屈曲或自旋轨道耦合时,二维节点线半金属态可能转变为二维狄拉克半金属态或二维拓扑晶体绝缘态。

英文摘要:

Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional (3D) Weyl semimetals, 3D Dirac semimetals, and 3D node-line semimetals. In particular, several compounds (e.g., certain three-dimensional graphene networks, Cu3PdN, Ca3P2) were discovered to be 3D node-line semimetals, in which the conduction and the valence bands cross at closed lines in the Brillouin zone. Except for the two-dimensional (2D) Dirac semimetal (e.g., in graphene), 2D topological semimetals are much less investigated. Here, we propose the new concept of a 2D node-line semimetal and suggest that this state could be realized in a new mixed lattice (we name it as HK lattice) composed by kagome and honeycomb lattices. We find that A3B2 (A is a group-IIB cation and B is a group-VA anion) compounds (such as Hg3As2) with the HK lattice are 2D node-line semimetals due to the band inversion between cation s orbital and anion pz orbital. In the presence of buckling or spin-orbit coupling, the 2D node-line semimetal state may turn into 2D Dirac semimetal state or 2D topological crystalline insulating state.

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