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arXiv 2103.06325cond-mat.supr-concond-mat.mtrl-sci
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超导kagome金属的电荷密度波和电子性质

Charge density waves and electronic properties of superconducting kagome metals

Hengxin Tan, Yizhou Liu, Ziqiang Wang, Binghai Yan

摘要:

Kagome金属$A$ V $_3$ Sb $_5$($A=$ K,Rb,and Cs)在低于$0.9 \sim 2.5 $ K的温度下表现出有趣的超导性,在$80\sim 100 $ K附近有电荷密度波(CDW)跃迁,以及$\mathbb{Z}_{2}$拓扑表面态。CDW相的性质及其与超导性的关系仍然难以捉摸。在这项工作中,我们研究的电子和结构的性质CDW的第一性原理计算。我们揭示了一个逆星大卫变形的$2\times2\times2$ CDW基态的戈薇晶格。kagome晶格显示软化呼吸声子模式,表明结构不稳定。然而,电子通过费米面嵌套和范霍夫奇点在CDW跃迁中起着至关重要的作用。大卫星结构的逆同意最近的实验,通过扫描隧道显微镜(STM)。CDW相继承了非平凡的$\mathbb{Z}_{2}$型拓扑能带结构。此外,我们发现,电子-声子耦合是太弱,占超导电性$T_c$在所有三种材料。这意味着这些戈薇金属存在非常规配对。我们的研究结果对了解可果美金属的超导电性和拓扑结构提供了必要的知识。

英文摘要:

Kagome metals $A$V$_3$Sb$_5$ ($A=$ K, Rb, and Cs) exhibit intriguing superconductivity below $0.9 \sim 2.5 $ K, a charge density wave (CDW) transition around $80\sim 100 $ K, and $\mathbb{Z}_{2}$ topological surface states. The nature of the CDW phase and its relation to superconductivity remains elusive. In this work, we investigate the electronic and structural properties of CDW by first-principles calculations. We reveal an inverse Star of David deformation as the $2\times2\times2$ CDW ground state of the kagome lattice. The kagome lattice shows softening breathing-phonon modes, indicating the structural instability. However, electrons play an essential role in the CDW transition via Fermi surface nesting and van Hove singularity. The inverse Star of David structure agrees with recent experiments by scanning tunneling microscopy (STM). The CDW phase inherits the nontrivial $\mathbb{Z}_{2}$-type topological band structure. Further, we find that the electron-phonon coupling is too weak to account for the superconductivity $T_c$ in all three materials. It implies the existence of unconventional pairing of these kagome metals. Our results provide essential knowledge toward understanding the superconductivity and topology in kagome metals.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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