Local spectroscopic evidence for a nodeless magnetic kagome superconductor CeRu₂

We report muon spin rotation (µSR) experiments on the microscopic properties of superconductivity and magnetism in the kagome superconductor CeRu₂ with T c ≃ 5 K. From the measurements of the temperature-dependent magnetic penetration depth λ, the superconducting order parameter exhibits nodeless pairing, which fits best to an anisotropic s-wave gap symmetry. We further show that the T c /λ ⁻² ratio is comparable to that of unconventional superconductors. Furthermore, the powerful combination of zero-field (ZF)-µSR and high-field µSR has been used to uncover magnetic responses across three characteristic temperatures, identified as T 1 ∗ ≃ 110 K, T 2 ∗ ≃ 65 K, and T 3 ∗ ≃ 40 K. Our experiments classify CeRu₂ as an exceedingly rare nodeless magnetic kagome superconductor.