电荷有序的 Kagome 金属 CsV$_3$Sb$_5$ 中的应变调谐节点超导性
Strain-Tuned Nodal Superconductivity in the Charge-Ordered Kagome Metal CsV$_3$Sb$_5$
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中文总结 AI 辅助
研究 Kagome 金属 CsV$_3$Sb$_5$ 中超导配对对称性及与 CDW 序关系，利用 $^{121}$Sb NQR 在原位单轴压力下研究超导演变，发现拉伸应变可独立调谐超导性，常压下简并超导态应变下分裂，证明单轴压力对超导性高度可调。
中文摘要 AI 辅助
Kagome 金属 CsV$_3$Sb$_5$ 中超导配对对称性的本质及其与电荷密度波（CDW）序的关系是尚未解决的核心问题。本文利用 $^{121}$Sb 核四极共振（NQR）研究了 CsV$_3$Sb$_5$ 在原位单轴压力下超导性的演变。发现拉伸应变显著提高超导转变温度 $T_{\rm c}$，而 CDW 不变，表明超导性可独立于体电荷序进行调谐。在拉伸应变 $\varepsilon$ = +0.90% 时，核自旋 - 晶格弛豫率显示出明显的双转变：在 $T_{\rm c1}$ = 3.6 K 处有一个向节点能隙态的上转变，在 $T_{\rm c2}$ = 3.0 K 处有一个以无节点能隙为特征的下转变。这些结果证明了常压下 Kagome 金属中具有不同能隙对称性的简并超导态在应变下会分裂。我们的工作证明了单轴压力对超导性具有高度可调性。
英文摘要
The nature of the superconducting pairing symmetry in the kagome metal CsV$_3$Sb$_5$ and its relationship with the charge density wave (CDW) order are central unresolved issues. Here, we investigate the evolution of superconductivity in CsV$_3$Sb$_5$ under in-situ uniaxial pressure using $^{121}$Sb nuclear quadrupole resonance (NQR). We find that tensile strain significantly enhances the superconducting transition temperature, $T_{\rm c}$, while the CDW remains unchanged, demonstrating that superconductivity can be tuned independently of the bulk charge order. At a tensile strain of $\varepsilon$ = +0.90%, the nuclear spin-lattice relaxation rate reveals a remarkable double transition: an upper transition at $T_{\rm c1}$ = 3.6 K to a nodal gap state, and a lower one at $T_{\rm c2}$ = 3.0 K characterized by a nodeless gap. These results evidence degenerate superconducting states with different gap symmetry in the kagome metal at ambient pressure which split under strain. Our work demonstrates a high tunability of superconductivity by uniaxial pressure.
