Unconventional superconducting gaps in a kagome metal

Kagome metals AV₃Sb₅ (A = K, Rb, Cs) exhibit a combination of topological band structures, van Hove singularities, and flat bands, giving rise to unconventional electronic and superconducting phenomena. In this talk, I will discuss our recent findings on the unconventional superconducting gaps in CsV₃Sb₅, revealed through electrical and heat transport and thermodynamic measurements [1]. In CsV₃Sb₅, where multiband superconductivity coexists with charge order, we identify two distinct superconducting regimes—surprisingly, without any clear phase transition separating them. These regimes exhibit remarkably different characteristics, including contrasting upper critical fields and angular-dependent thermal conductivity. The lower-temperature regime features an additional gap and hosts low-energy quasiparticles, possibly originating from a nodal gap structure. I will conclude with a theoretical perspective on these observations. This talk is based on our recent paper: [1]. M. S. Hossain et al., Unconventional gapping behaviour in a kagome superconductor, Nat. Phys. 21, 556–563 (2025).