Shang Tian, Zhao Jianzhou, Hu Lun-Hui, Wu Weikang, Xia Keqi, Ajeesh Mukkattu O, Nicklas Michael, Xu Yang, Zhan Qingfeng, Gawryluk Dariusz J, Shi Ming, Shiroka Toni
Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University, Shanghai, 200241, China.
Chongqing Key Laboratory of Precision Optics, Chongqing Institute of East China Normal University, Chongqing, 401120, China.
Adv Mater. 2025 Aug 21:e11385. doi: 10.1002/adma.202511385.
Chiral crystals, whose key feature is the structural handedness, host exotic quantum phenomena driven by the interplay of band topology, spin-orbit coupling (SOC), and electronic correlations. Due to the limited availability of suitable chiral-crystal materials, their unconventional superconductivity (SC) remains largely unexplored. Here, the discovery of unconventional SC in the La(Rh,Ir)Si family of materials is reported by combining muon-spin spectroscopy, band-structure calculations, and perturbation theory. This family, characterized by a double-helix chiral structure, hosts exotic multifold fermions that are absent in other topological chiral crystals. While LaRhSi behaves as a fully-gapped superconductor, the substitution of 4d-Rh by 5d-Ir significantly enhances the SOC and leads to the emergence of topological nodal-line SC in LaIrSi. The developed model shows that the nodal-line SC arises from an isotropic SOC with a specific strength. Such an exotic mechanism expands the conventional understanding of material candidates for unconventional SC, which typically rely on a significantly anisotropic SOC to promote the triplet pairing. The current work establishes a new type of phase diagram, which provides a comprehensive roadmap for identifying and engineering unconventional SC in chiral crystals. Furthermore, it calls for renewed investigations of unconventional SC in other widely studied superconductors with a chiral structure.
手性晶体的关键特征是结构手性，它承载着由能带拓扑、自旋轨道耦合（SOC）和电子关联相互作用驱动的奇异量子现象。由于合适的手性晶体材料数量有限，其非常规超导性（SC）在很大程度上仍未得到探索。在此，通过结合μ子自旋光谱、能带结构计算和微扰理论，报道了在La(Rh,Ir)Si族材料中发现非常规超导性。该族材料以双螺旋手性结构为特征，拥有其他拓扑手性晶体中不存在的奇异多重费米子。虽然LaRhSi表现为完全能隙超导体，但用5d-Ir替代4d-Rh会显著增强SOC，并导致LaIrSi中出现拓扑节线超导。所建立的模型表明，节线超导源于具有特定强度的各向同性SOC。这种奇异机制扩展了对非常规超导候选材料的传统认识，传统认识通常依赖于显著的各向异性SOC来促进三重态配对。当前的工作建立了一种新型相图，为识别和设计手性晶体中的非常规超导提供了全面的路线图。此外，它呼吁对其他广泛研究的具有手性结构的超导体中的非常规超导进行重新研究。
