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arXiv 1704.00697cond-mat.mtrl-sci
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Half-Heusler合金LiBaBi:一种新的五重能带简并拓扑半金属

Half-Heusler alloy LiBaBi: A new topological semimetal with five-fold band degeneracy

Mighfar Imam, Abhishek K. Singh

摘要:

基于第一性原理研究,我们发现了一种新的半Heusler相的拓扑半金属LiBaBi。这种反转对称破缺材料的显著特征是它仅由简单的$s$ -和$p$ -块元素组成。有趣的是,该材料在没有自旋轨道耦合(SOC)的情况下是普通的绝缘体,而当包括SOC时,成为表面拓扑半金属,显示鼓面态。这与其他的半金属线和半金属面形成鲜明对比,在这些半金属中,一旦包含SOC,扩展的节点结构就会被破坏。重要的是,线性能带交叉在费米能级附近具有三、四、五和六倍的简并性,使得这种化合物对于研究“非常规”费米子非常有吸引力。带交叉点在费米能级处形成围绕带中心的三维节点结构。我们确定负责的鼓面状态的外观的表面状态。该合金还显示出一个相变从拓扑半金属到一个平凡的绝缘体上施加的压力。除了揭示SOC对节点结构的有趣影响外,我们的研究结果还在拓扑半金属家族中引入了一种新的半Heusler合金,从而为实验探索创造了更多途径。

英文摘要:

Based on first-principles study, we report the finding of a new topological semimetal LiBaBi in half-Heusler phase. The remarkable feature of this nonmagnetic, inversion-symmetry-breaking material is that it consists of only simple $s$- and $p$-block elements. Interestingly, the material is ordinary insulator in the absence of spin-orbit coupling (SOC) and becomes nodal-surface topological semimetal showing drumhead states when SOC is included. This is in stark contrast to other nodal-line and nodal-surface semimetals, where the extended nodal structure is destroyed once SOC is included. Importantly, the linear band crossings host three-, four-, five- and six-fold degeneracies near the Fermi level, making this compound very attractive for the study of `unconventional' fermions. The band crossing points form a three-dimensional nodal structure around the zone center at the Fermi level. We identify the surface states responsible for the appearance of the drumhead states. The alloy also shows a phase transition from topological semimetal to a trivial insulator on application of pressure. In addition to revealing an intriguing effect of SOC on the nodal structure, our findings introduce a new half-Heusler alloy in the family of topological semimetals, thus creating more avenues for experimental exploration.

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