Mielke C, Das D, Yin J-X, Liu H, Gupta R, Jiang Y-X, Medarde M, Wu X, Lei H C, Chang J, Dai Pengcheng, Si Q, Miao H, Thomale R, Neupert T, Shi Y, Khasanov R, Hasan M Z, Luetkens H, Guguchia Z
Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen PSI, Switzerland.
Physik-Institut, Universität Zürich, Winterthurerstrasse 190, Zürich, Switzerland.
Nature. 2022 Feb;602(7896):245-250. doi: 10.1038/s41586-021-04327-z. Epub 2022 Feb 9.
The kagome lattice, which is the most prominent structural motif in quantum physics, benefits from inherent non-trivial geometry so that it can host diverse quantum phases, ranging from spin-liquid phases, to topological matter, to intertwined orders and, most rarely, to unconventional superconductivity. Recently, charge sensitive probes have indicated that the kagome superconductors AVSb (A = K, Rb, Cs) exhibit unconventional chiral charge order, which is analogous to the long-sought-after quantum order in the Haldane model or Varma model. However, direct evidence for the time-reversal symmetry breaking of the charge order remains elusive. Here we use muon spin relaxation to probe the kagome charge order and superconductivity in KVSb. We observe a noticeable enhancement of the internal field width sensed by the muon ensemble, which takes place just below the charge ordering temperature and persists into the superconducting state. Notably, the muon spin relaxation rate below the charge ordering temperature is substantially enhanced by applying an external magnetic field. We further show the multigap nature of superconductivity in KVSb and that the [Formula: see text] ratio (where T is the superconducting transition temperature and λ is the magnetic penetration depth in the kagome plane) is comparable to those of unconventional high-temperature superconductors. Our results point to time-reversal symmetry-breaking charge order intertwining with unconventional superconductivity in the correlated kagome lattice.
Kagome晶格是量子物理学中最显著的结构基元，因其固有的非平凡几何结构而受益，从而能够容纳多种量子相，从自旋液体相到拓扑物质，再到交织序，以及极为罕见的非常规超导性。最近，电荷敏感探针表明，Kagome超导体AVSb（A = K、Rb、Cs）表现出非常规的手性电荷序，这类似于霍尔丹模型或瓦尔马模型中人们长期寻找的量子序。然而，电荷序的时间反演对称性破缺的直接证据仍然难以捉摸。在此，我们使用μ子自旋弛豫来探测KVSb中的Kagome电荷序和超导性。我们观察到μ子系综所感知的内场宽度有显著增强，这种增强刚好发生在电荷有序温度以下，并持续到超导态。值得注意的是，在电荷有序温度以下，施加外部磁场会显著提高μ子自旋弛豫率。我们进一步展示了KVSb中超导性的多能隙性质，并且[公式：见原文]比率（其中T是超导转变温度，λ是Kagome平面中的磁穿透深度）与非常规高温超导体的相当。我们的结果表明，在相关的Kagome晶格中，时间反演对称性破缺的电荷序与非常规超导性相互交织。
