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arXiv 2009.00849cond-mat.mtrl-scicond-mat.mes-hallcond-mat.supr-con
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2M WS $_2$的拓扑性质:第一性原理研究

Topological Properties of Bulk and Bilayer 2M WS$_2$: A First-Principles Study

Nesta Benno Joseph, Awadhesh Narayan

摘要:

最近发现的体相WS $_2$的2M相被观察到具有超导性,其临界温度为8.8 K,是超导过渡金属二硫属化物中最高的。还预测支持受保护的表面状态,它可能是一个潜在的拓扑超导体。在本研究中,我们进行了详细的第一性原理分析散装和双层2M WS $_2$。我们报告的体相的全面调查,比较从不同的交换相关泛函的实验报告值的结构和电子性质。通过对$Z_2$不变量和表面态的计算,我们支持了它的非平凡能带性质。基于体相分析的结果,我们预测双层2M WS $_2$是一种新的二维拓扑材料。我们从第一性原理声子计算证明了它的动力学稳定性,并给出了它的电子性质,突出了W $d$和S $p$状态之间的带反转。通过$Z_2$不变的计算和计算的边缘状态,我们表明,双层2M WS $_2$具有保护,强大的边缘状态。在这个新提出的双层反转对称性破缺也导致了Berry曲率偶极子的存在和由此产生的非线性响应。我们计算了Berry曲率分布和偶极子作为费米能量的函数。我们建议,BCD信号,这是不存在于中心对称的散装2M WS $_2$,可以是双分子层的签名。我们希望我们的预测能够导致这种尚未发现的二维拓扑材料的实验实现。

英文摘要:

Recently discovered 2M phase of bulk WS$_2$ was observed to exhibit superconductivity with a critical temperature of 8.8 K, the highest reported among superconducting transition metal dichalcogenides. Also predicted to support protected surface states, it could be a potential topological superconductor. In the present study, we perform a detailed first-principles analysis of bulk and bilayer 2M WS$_2$. We report a comprehensive investigation of the bulk phase, comparing structural and electronic properties obtained from different exchange correlation functionals to the experimentally reported values. By calculation of the $Z_2$ invariant and surface states, we give support for its non-trivial band nature. Based on the insights gained from the analysis of the bulk phase, we predict bilayer 2M WS$_2$ as a new two-dimensional topological material. We demonstrate its dynamical stability from first-principles phonon computations and present its electronic properties, highlighting the band inversions between the W $d$ and S $p$ states. By means of $Z_2$ invariant computations and a calculation of the edge states, we show that bilayer 2M WS$_2$ exhibits protected, robust edge states. The broken inversion symmetry in this newly proposed bilayer also leads to the presence of Berry curvature dipole and resulting non-linear responses. We compute the Berry curvature distribution and the dipole as a function of Fermi energy. We propose that BCD signals, which are absent in the centrosymmetric bulk 2M WS$_2$, can be signatures of the bilayer. We hope our predictions lead to the experimental realization of this as-yet-undiscovered two-dimensional topological material.

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