Impact of charge-density-wave pattern on the superconducting gap in Vanadium-based kagome superconductors

Kagome metals AV₃Sb₅ (A = K, Rb, Cs) provide a compelling platform to explore the interplay between superconductivity (SC) and charge-density-wave (CDW) orders. While distinct CDW orders have been identified in K/RbV₃Sb₅ versus CsV₃Sb₅, their influence on the SC order parameter remains unresolved. Here, we investigate low-energy quasiparticle excitations in AV₃Sb₅, uncovering a striking difference in SC gap anisotropy: K/RbV₃Sb₅ exhibit fully gapped, nearly isotropic s-wave states, in contrast to the strongly anisotropic SC gap in CsV₃Sb₅. Impurity scattering introduced via electron irradiation in K/RbV₃Sb₅ has a minimal impact on low-energy excitations, and it induces an increase in the SC transition temperature T_c, consistent with more isotropic s-wave SC competing with CDW order. Our theoretical analysis attributes the observed SC gap anisotropy differences to distinct CDW modulation patterns: the star-of-David structure unique to CsV₃Sb₅ preserves van Hove singularities near the Fermi level, promoting anisotropic s-wave SC with enhanced T_c via bond-order fluctuations. These findings establish a systematic framework for understanding the interplay between SC and CDW orders in AV₃Sb₅, driven by electron correlations.