Magnetic correlations and superconducting pairing near higher-order Van Hove singularities

Abstract: We explore magnetic correlations and superconducting pairing near higher-order Van Hove singularities in an extended Hubbard model on honecycomb lattice incorporating third-nearest-neighbor hopping ( t'' ). Using quantum Monte Carlo methods, we identify a crossover between ferromagnetic and antiferromagnetic fluctuations near higher-order Van Hove singularities filling, where ( t'' ) enhances ferromagnetic correlations below while suppressing antiferromagnetic fluctuations toward half-filling. At low doping, ( f_n )-wave pairing dominates, amplified by higher-order Van Hove singularities-induced divergent density of states. Remarkably, despite general suppression of ( f_n )-wave pairing by increasing next-nearest neighbor hopping ( t' ) and ( t'' ), a critical ( t'' = 0.15 ) triggers anomalous enhancement via higher-order Van Hove singularities renormalization at a fix $t'$. The nearest-neighbor Coulomb interactions ( V ) suppress superconducting correlation, which exhibiting sign-independent suppression proportional to ( |V| ). These results highlight the interplay of higher-order Van Hove singularities-driven electronic structure, magnetic fluctuations, and pairing symmetry competition in electron correlated systems.