Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
Department of Physics, Fuzhou University, Fuzhou, Fujian, 350108, China.
Nat Commun. 2023 Jun 28;14(1):3819. doi: 10.1038/s41467-023-39500-7.
Van Hove singularity (VHS) has been considered as a driving source for unconventional superconductivity. A VHS in two-dimensional (2D) materials consists of a saddle point connecting electron-like and hole-like bands. In a rare case, when a VHS appears at Fermi level, both electron-like and hole-like conduction can coexist, giving rise to an enhanced density of states as well as an attractive component of Coulomb interaction for unconventional electronic pairing. However, this van Hove scenario is often destroyed by an incorrect chemical potential or competing instabilities. Here, by using angle-resolved photoemission measurements, we report the observation of a VHS perfectly aligned with the Fermi level in a kagome superconductor CsVTaSb (x ~ 0.4), in which a record-high superconducting transition temperature is achieved among all the current variants of AVSb (A = Cs, Rb, K) at ambient pressure. Doping dependent measurements reveal the important role of van Hove scenario in boosting superconductivity, and spectroscopic-imaging scanning tunneling microscopy measurements indicate a distinct superconducting state in this system.
范霍夫奇点（VHS）被认为是非常规超导的驱动力。二维（2D）材料中的 VHS 由连接电子型和空穴型能带的鞍点组成。在极少数情况下，当 VHS 出现在费米能级时，电子型和空穴型传导可以共存，从而导致态密度增强以及库仑相互作用的吸引分量增加，从而产生非常规的电子配对。然而，这种范霍夫情景经常由于不正确的化学势或竞争不稳定性而被破坏。在这里，我们通过角分辨光发射测量报告了在 kagome 超导体 CsVTaSb（x~0.4）中完美与费米能级对齐的 VHS 的观察结果，在常压下，它在所有当前 AVSb（A=Cs、Rb、K）变体中实现了创纪录的高温超导转变温度。掺杂依赖性测量揭示了范霍夫情景在提高超导性方面的重要作用，光谱成像扫描隧道显微镜测量表明该体系中存在明显的超导状态。
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