Roppongi Masaki, Cai Yipeng, Ogawa Koki, Liu Supeng, Zhao Guoqiang, Oudah Mohamed, Fujii Takenori, Imamura Kumpei, Fang Shengjie, Ishihara Kota, Hashimoto Kenichiro, Matsuura Kohei, Mizukami Yuta, Pula Mathew, Young Cyrus, Marković Igor, Bonn Douglas A, Watanabe Takao, Yamashita Aichi, Mizuguchi Yoshikazu, Luke Graeme M, Kojima Kenji M, Uemura Yasutomo J, Shibauchi Takasada
Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba, 277-8561, Japan.
RIKEN Center for Quantum Computing, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan.
Nat Commun. 2025 Jul 23;16(1):6573. doi: 10.1038/s41467-025-61651-y.
Time-reversal symmetry breaking (TRSB) in magnetic topological insulators induces a Dirac gap in the topological surface state (TSS), leading to exotic phenomena such as the quantum anomalous Hall effect. Yet, the interplay between TRSB and topology in superconductors remains underexplored due to limited suitable materials. Here we employ zero-field muon spin relaxation (μSR) as a sensitive probe of TRSB to map out the electronic phase diagrams of iron-chalcogenide superconductors FeSeTe. For the Te composition x = 0.64 with the highest superconducting transition temperature T = 14.5 K, which is known to host a TSS and Majorana zero modes within vortices, we detect spontaneous magnetic fields below T distinct from a magnetic order. This signifies a TRSB superconducting state in the bulk, revealing the convergence of unconventional TRSB superconductivity with topologically nontrivial electronic structures in FeSeTe. Given the relatively high T and the tunability of the Fermi level through chemical substitution, iron-chalcogenide superconductors offer an intriguing platform for investigating the synergy between topological superconductivity and TRSB.
磁性拓扑绝缘体中的时间反演对称性破缺（TRSB）会在拓扑表面态（TSS）中诱导出狄拉克能隙，从而导致诸如量子反常霍尔效应等奇异现象。然而，由于合适的材料有限，超导体中TRSB与拓扑之间的相互作用仍未得到充分探索。在这里，我们采用零场μ子自旋弛豫（μSR）作为TRSB的灵敏探针，来绘制铁硫族超导体FeSeTe的电子相图。对于Te组分为x = 0.64且具有最高超导转变温度T = 14.5 K的样品（已知其在涡旋中存在TSS和马约拉纳零模），我们在低于T的温度下检测到了不同于磁有序的自发磁场。这表明在体相中存在TRSB超导态，揭示了FeSeTe中非常规TRSB超导性与拓扑非平凡电子结构的趋同。鉴于相对较高的T以及通过化学取代对费米能级的可调性，铁硫族超导体为研究拓扑超导性与TRSB之间的协同作用提供了一个有趣的平台。
