Interplay of competing bond-order and loop-current fluctuations as a possible mechanism for superconductivity in kagome metals

The pairing symmetry and underlying mechanism for superconducting state of AV3Sb5 (A=K, Rb, Cs) kagome metal is the focus of considerable research efforts. In this study we investigate the superconductivity in these kagome metal mediated by the interplay between fluctuating bond orders and loop currents. First, we consider an 8-band minimal model, which includes V and the two types of Sb - both within and above/below the kagome plane. This model captures the Fermi surface pocket with significant in-plane Sb contribution near the zone center and reproduces the two types of van Hove singularities (VHS), one of which has a strong out of plane Sb weight. By incorporating nearest-neighbor Coulomb interactions between V–V and V–planar Sb sites in our minimal 8-band model, we compute the RPA-corrected susceptibilities for fluctuating bond orders and loop currents in both charge and spin channels and examine the resulting superconducting instabilities arising from their interplay. In particular, we find that time-reversal odd charge loop-current fluctuations favor unconventional pairing symmetries such as s+- or chiral d+id, whereas time-reversal even charge–bond order fluctuations stabilize conventional s-wave​ pairing. Finally, we discuss how the gap functions obtained from our calculations are consistent with recent experimental observations.