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arXiv · 2506.03509

Multiband superconductivity in the topological Kramers nodal-line semimetals

Tian Shang·Jianzhou Zhao·Keqi Xia·Lun-Hui Hu·Yang Xu·Qingfeng Zhan·Dariusz Jakub Gawryluk·Toni Shiroka
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Abstract

Recent band-structure calculations predict that the ruthenium-based ternary silicides are three-dimensional Kramers nodal line semimetals. Among them, NbRuSi and TaRuSi show bulk superconductivity (SC) below $T_c \sim 3$ K and 4 K, as well as spontaneous magnetic fields. The latter indicates the breaking of time-reversal symmetry and, thus, unconventional SC in both compounds. Previous temperature-dependent muon-spin spectroscopy studies failed to distinguish whether such compounds exhibit single-gap or multi-gap SC. Here, we report on systematic measurements of the field-dependent muon-spin relaxation rates in the superconducting state and on temperature-dependent electrical resistivity and specific heat under applied magnetic fields. Both the upper critical field and the field-dependent superconducting relaxation are well described by a two-band model. By combining our experimental results with numerical band-structure calculations, we provide solid evidence for multiband SC in NbRuSi and TaRuSi, and thus offer further insight into the unconventional- and topological nature of their superconductivity.

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Tian Shang, Jianzhou Zhao, Keqi Xia, Lun-Hui Hu, Yang Xu, Qingfeng Zhan, Dariusz Jakub Gawryluk, Toni Shiroka. 2025-06-04. Multiband superconductivity in the topological Kramers nodal-line semimetals. https://doi.org/10.1103/k2t5-wcq1

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