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

TL;DR

This paper explores how higher-order Van Hove singularities influence magnetic fluctuations and superconducting pairing in honeycomb lattices, revealing a crossover from ferromagnetic to antiferromagnetic dominance and conditions that enhance unconventional superconductivity.

Contribution

It uncovers the universal magnetic crossover and the enhancement of f-wave pairing near higher-order Van Hove singularities, providing insights into band engineering in graphene-like materials.

Findings

Ferromagnetic fluctuations dominate below the Van Hove filling.

Antiferromagnetic fluctuations take over near half filling.

Higher-order Van Hove singularities enhance f-wave pairing.

Abstract

Higher-order Van Hove singularities in strongly correlated electron systems provide a fertile ground for emergent electronic orders and superconductivity. This study investigates the interplay between magnetic fluctuations and superconducting pairing near higher-order Van Hove singularities on the honeycomb lattice, a paradigmatic platform relevant to graphene. By incorporating third-nearest-neighbor hopping \(t''\), we uncover a universal crossover: ferromagnetic fluctuations dominate below the higher-order Van Hove filling, while antiferromagnetic fluctuations take over toward half filling. A key finding is that the already dominant \(f_n\)-wave pairing is enhanced in the critical region of this magnetic crossover by the higher-order Van Hove. This enhancement is driven by the synergistic effect of the higher-order Van Hove singularities-induced divergent density of states and the competing magnetic fluctuations. Although increased hopping parameters generally suppress superconducting correlation, we identify a critical \(t''\) that anomalously enhances pairing via the higher-order Van Hove renormalization. Furthermore, the nearest-neighbor Coulomb interaction suppresses the pairing correlation function in a sign-independent manner. Our results clarify the competitive mechanisms between magnetic fluctuations and unconventional superconductivity in higher-order Van Hove singularities systems, offering a theoretical basis for tailoring quantum phases in graphene-based materials via band engineering.