扭曲砖相变金属单硫族化物中的非中心对称外尔半金属态和应变效应,Nanoscale

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扭曲砖相变金属单硫族化物中的非中心对称外尔半金属态和应变效应
Nanoscale ( IF 5.8 ) Pub Date : 2023-01-12 , DOI: 10.1039/d2nr04946e
Jia-Fang Wu ₁ , Sha-Sha Ke ₁ , Yong Guo ₂ , Huai-Wu Zhang ₁ , Hai-Feng Lü _{1,

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Affiliation

外尔半金属是一类打破时间反转或反转对称性的无带隙电子激发拓扑量子材料。在这里，我们从理论上证明了非中心对称扭曲砖相 MoTe 中外尔半金属态的存在。基于第一性原理计算和基于 Wannier 的紧束缚方法，系统地研究了 MoTe 的拓扑性质和应变效应。在没有自旋轨道耦合 (SOC) 的情况下，MoTe 表现出与镜面反射对称性相关的无间隙节点环状态。当 SOC 打开时，两个节点环分裂成 22 对具有相反手性的外尔点 (WP)。当单轴 ( ε _z) 考虑到应变，MoTe 的 Weyl 半金属相显示出极大的稳健性和惊人的可调拓扑强度。特别是，WP 的总数在压力下发生了显着变化。+4% 和 +8% 单轴应变下的 MoTe 只有四对 WP，在动量空间中具有相对较大的分离。这些结果表明，弱应变下的 MoTe 是一种很有前途的部分理想的 I 型 Weyl 半金属候选者，而同系物结构 WTe 在有和没有 SOC 的情况下都打开了直接间隙，显示出补偿的半金属状态。

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Non-centrosymmetric Weyl semimetal state and strain effect in the twisted-brick phase transition metal monochalcogenides

Weyl semimetals are a class of gapless electronic excitation topological quantum materials upon breaking time-reversal or inversion symmetry. Here, we demonstrate the existence of the Weyl semimetal state in the non-centrosymmetric twisted-brick phase MoTe theoretically. The topological properties and strain effects of MoTe have been systematically studied based on first-principles calculations and the Wannier-based tight-binding method. In the absence of spin–orbit coupling (SOC), MoTe exhibits gapless nodal loop states related to the mirror reflection symmetry. When the SOC is turned on, the two nodal loops split into 22 pairs of Weyl points (WPs) with opposite chirality. When the effect of uniaxial (ε_z) strain is taken into account, the Weyl semimetal phase of MoTe shows great robustness and striking tunable topological strength. In particular, the total number of WPs changes significantly under strain. MoTe under +4% and +8% uniaxial strains have only four pairs of WPs with a relatively large separation in momentum space. These results show that MoTe under weak strain is a promising partly ideal type I Weyl semimetal candidate, while the isolog structure WTe both opens a direct gap with and without SOC, showing a compensated semimetal state.

更新日期：2023-01-12

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