Graham J N, Liu H, Sazgari V, Mielke Iii C, Medarde M, Luetkens H, Khasanov R, Shi Y, Guguchia Z
PSI Center for Neutron and Muon Sciences CNM, 5232 Villigen PSI, Switzerland.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190 China.
Commun Mater. 2024;5(1):225. doi: 10.1038/s43246-024-00666-2. Epub 2024 Oct 12.
The two-dimensional kagome lattice is an experimental playground for novel physical phenomena, from frustrated magnetism and topological matter to chiral charge order and unconventional superconductivity. A newly identified kagome superconductor, TaVSi has recently gained attention for possessing a record high critical temperature, = 7.5 K for kagome metals at ambient pressure. In this study we conducted a series of muon spin rotation measurements to delve deeper into understanding the superconducting and normal state properties of TaVSi. We demonstrate that TaVSi is a bulk superconductor with either a s+s-wave or anisotropic s-wave gap symmetry, and has an unusual paramagnetic shift in response to external magnetic fields in the superconducting state. Additionally, we observe an exceptionally low superfluid density - a distinctive characteristic of unconventional superconductivity - which remarkably is comparable to the superfluid density found in hole-doped cuprates. In its normal state, TaVSi exhibits a significant increase in the zero-field muon spin depolarisation rate, starting at approximately 150 K, which has been observed in other kagome-lattice superconductors, and therefore hints at possible hidden magnetism. These findings characterise TaVSi as an unconventional superconductor and a noteworthy new member of the vanadium-based kagome material family.
二维 Kagome 晶格是一个用于研究新型物理现象的实验平台，涵盖了从受挫磁性、拓扑物质到手性电荷序和非常规超导性等领域。一种新发现的 Kagome 超导体 TaVSi 最近因其在环境压力下具有创纪录的高温临界温度（对于 Kagome 金属而言，Tc = 7.5 K）而备受关注。在本研究中，我们进行了一系列μ子自旋旋转测量，以更深入地了解 TaVSi 的超导和正常态特性。我们证明 TaVSi 是一种体超导体，具有 s + s 波或各向异性 s 波能隙对称性，并且在超导态下对外加磁场有异常的顺磁位移。此外，我们观察到其超流密度极低——这是非常规超导性的一个显著特征——值得注意的是，该超流密度与空穴掺杂铜酸盐中的超流密度相当。在正常态下，TaVSi 从大约 150 K 开始，零场μ子自旋去极化率显著增加，这在其他 Kagome 晶格超导体中也有观察到，因此暗示可能存在隐藏磁性。这些发现表明 TaVSi 是一种非常规超导体，也是钒基 Kagome 材料家族中一个值得关注的新成员。
