Distinct Uniaxial Stress and Pressure Fingerprint of Superconductivity in the 3D Kagome Lattice Compound CeRu2

Abstract

The exploration of tunable superconductivity in strongly correlated electron systems is a central pursuit in condensed matter physics, with implications for both fundamental understanding and potential applications. The Laves phase CeRu$_{2}$, a pyrochlore compound, exhibits a three-dimensional (3D) Kagome lattice type geometry giving rise to flat bands and degenerate Dirac points, where band structure features intertwine with strong multi-orbital interaction effects deriving from its correlated electronic structure. Here, we combine muon spin rotation ($\mu$SR), uniaxial in-plane stress, and hydrostatic pressure to probe the superconducting state of CeRu$_{2}$. Uniaxial stress up to 0.22 GPa induces a dome-shaped evolution of the critical temperature $T_{\rm c}$, with an initial plateau, successively followed by enhancement and suppression without any structural phase transition. Stress is further found to drive a crossover from anisotropic to isotropic $s$-wave pairing. In contrast, hydrostatic pressure up to 2.2 GPa leaves $T_{\rm c}$ largely unchanged but alters the superfluid density from exponential to linear behavior at low temperatures, indicative of nodal superconductivity under hydrostatic pressure. Taken together, these results indicate that CeRu$_{2}$ occupies an ideal position in parameter space, enabling highly responsive and multifold tunability of superconductivity in this three-dimensional correlated electronic system. This warrants further quantitative analysis of the interplay between lattice geometry, electronic correlations, and pairing symmetry.