摘要
Based on irreducible representations(or symmetry eigenvalues) and compatibility relations(CR), a material can be predicted to be a topological/trivial insulator(satisfying CR) or a topological semimetal(violating CR). However, Weyl semimetals(WSMs) usually go beyond this symmetry-based strategy. In other words, Weyl nodes could emerge in a material, no matter if its occupied bands satisfy CR, or if the symmetry indicators are zero. In this work, we propose a new topological invariant v for the systems with S4 symmetry(i.e., the improper rotation S_(4)(≡IC_(4z)) is a proper fourfold rotation(C_(4z)) followed by inversion(I)), which can be used to diagnose the WSM phase. Moreover, v can be easily computed through the onedimensional Wilson-loop technique. By applying this method to the high-throughput screening in our first-principles calculations, we predict a lot of WSMs in both nonmagnetic and magnetic compounds.Various interesting properties(e.g., magnetic frustration effects, superconductivity and spin-glass order,etc.) are found in predicted WSMs, which provide realistic platforms for future experimental study of the interplay between Weyl fermions and other exotic states.
基于对称性的不可约表示和相容性关系,人们可以将材料分为拓扑(或平庸)绝缘体(满足相容性关系),或是拓扑半金属(不满足相容性关系).但对于外尔半金属的判断通常超出了这种基于对称性方法的能力.换句话说,不论材料中占据态能带满不满足相容性关系,或者对称性指标是否为零,外尔点都可能出现在该材料中.本文针对具有S4对称性的体系提出了一种新型的拓扑不变量χ,并以此来检测体系中是否有外尔点的存在.χ可以通过一维Wilson-loop方法计算出来.将这种方法应用到高通量第一性原理计算中,作者在非磁和磁性体系中预测了大量新的外尔半金属材料.这些新发现的拓扑半金属材料具有许多独特的性质,如磁阻挫效应、超导和自旋玻璃态等.这些材料为外尔费米子和各种奇异物态之间相互作用研究提供了平台.
作者
Jiacheng Gao
Yuting Qjan
Simin Nie
Zhong Fang
Hongming Weng
Zhijun Wang
高嘉成;钱玉婷;聂思敏;方忠;翁红明;王志俊(Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China;Department of Materials Science and Engineering,Stanford University,Stanford CA 94305,USA)
基金
supported by the National Natural Science Foundation of China (11974395,11674369, and 11925408)
the Strategic Priority Research Program of Chinese Academy of Sciences (CAS XDB33000000)
the Center for Materials Genome
support from the National Key Research and Development Program of China (2016YFA0300600, 2016YFA0302400, and 2018YFA0305700)
the K. C. Wong Education Foundation (GJTD-2018-01)。
