Superconductivity in multiorbital systems with repulsive interactions: Hund's pairing versus spin-fluctuation pairing

Hund's pairing refers to Cooper generated by onsite interactions that become attractive due large exchange $J$. This is possible in multiorbital systems even when all local bare are repulsive, since attractions specific channels given certain linear combinations of interaction parameters. On the other hand, processes such as spin fluctuations also present. We compare mean-field and spin-fluctuation-mediated using electronic bands appropriate for different classes over a wide range find that, without clear nesting features, superconducting state mechanism agrees well with from full fluctuation vertex spin-orbit coupling sufficiently large. characterized peaked finite-momentum particle-hole susceptibility, spin-fluctuation generally dominates pairing. From this perspective states appear unlikely be realized like ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ generic iron-based superconductors.