[论文解读] Anisotropic proximity-induced superconductivity and edge supercurrent in Kagome metal, K1-xV3Sb5

Yaojia Wang, S. Y. Yang+12 more|arXiv (Cornell University)|Dec 10, 2020

Advanced Condensed Matter Physics参考文献 51被引用 45

一句话总结

该论文展示了在 K1-xV3Sb5 结-Josephson 结中的各向异性近邻诱导超导性，揭示了方向相关的磁电阻和边缘态驱动电流的证据。它还提出一种可能有利于自旋三重态配对的各向异性内部磁场。

ABSTRACT

Materials with transition metals in triangular lattices are of great interest for their potential combination of strong correlation, exotic magnetism and electronic topology. Kagome nets are of particular importance since the discovery of geometrically frustrated magnetism and topological band structures in crystals like Herbertsmithite and Fe3Sn2, respectively. KV3Sb5 was discovered to be a layered topological metal with a Kagome net of vanadium. Here, we fabricated Josephson Junctions (JJ) of K1-xV3Sb5 and induced superconductivity over long junction lengths. Through magnetoresistance and current vs. phase measurements, we observed magnetic field sweeping direction dependent magnetoresistance, and an anisotropic interference pattern with a Fraunhofer pattern for in-plane magnetic field, but a suppression of critical current for out-of-plane magnetic field. These results indicate an anisotropic internal magnetic field in K1-xV3Sb5 which influences the superconducting coupling in the junction, possibly giving rise to spin-triplet superconductivity. In addition, the observation of long-lived fast oscillations shows evidence of spatially localized conducting channels arising from edge states. These observations pave the way for studying unconventional superconductivity and Josephson device based on Kagome metals with electron correlation and topology.

研究动机与目标

• 激发在具有强相关性与拓扑性的 Kagome 金属中探索超导性的兴趣。
• 在基于 K1-xV3Sb5 的约瑟夫森结中，研究跨越较长的结长度的近邻诱导超导性。
• 识别指示非传统配对或边缘态的磁场相关传输特征。

提出的方法

• 使用 K1-xV3Sb5 制作约瑟夫森结，以在较长的结长度上诱导超导性。
• 在变化的平行场与垂直场下进行磁阻测量。
• 开展电流对相位 (I–φ) 测量，以绘制干涉图样。
• 分析场方向的依赖性，以推断影响耦合的内部磁场各向异性。
• 寻找快速振荡和与边缘通道相关的传输特征。

实验结果

研究问题

• RQ1 K1-xV3Sb5 在约瑟夫森结中是否表现出各向异性的磁场相关超导耦合？
• RQ2 在近邻诱导超导性下，K1-xV3Sb5 的边缘态是否能够承载空间上局域化、寿命较长的边缘电流？
• RQ3 是否有证据表明由材料的内部磁场与拓扑性引发的非常规（潜在的自旋三重态）配对？

主要发现

• 磁场方向控制磁阻，在结中显示出各向异性传输。
• 平行场产生 Fraunhofer 样干涉图样，而垂直场则抑制临界电流。
• 证据表明存在各向异性的内部磁场，可影响结中的超导耦合。
• 观测到寿命较长的快速振荡，表明存在与边缘态可能相关的空间局域导电通道。
• 结果指向 Kagome 金属在具相关性与拓扑性方面的潜在非常规超导性。