Loop-current fluctuations mediated chiral d-wave pairing in kagome lattice

Recent various experiments have provided evidence supporting the emergence of loop current order in kagome metals. Particularly superconductivity in AV₃Sb₅ is significantly enhanced when this charge order is suppressed by pressure or doping. Distinct from magnetic order, loop current order does not couple directly to spin and thus whether such fluctuations can enhance superconductivity remains elusive. In this work, we design a sign problem-free bilayer kagome model coupled to quantum Ising spins through bond currents and perform determinant quantum Monte Carlo simulations to explore single-particle properties and superconductivity arising from 2 × 2 loop-current fluctuations. We find that this loop current order induces intriguing band folding, band broadening and gap opening around saddle points. Remarkably, our pairing susceptibility analysis identifies a dominant enhancement of superconductivity due to loop-current fluctuations, with the dominant pairing being the chiral d-wave channel. This pairing primarily occurs within the intra-sublattice channel and involves third nearest-neighbor sites, attributed to the unique sublattice texture associated with van Hove singularities. We also discuss potential experimental implications for kagome superconductors.