Theory of the spin-triplet superconductivity in Sr2RuO4 based on perturbation approach to three-band Hubbard model

We investigate a mechanism of the spin-triplet superconductivity in Sr₂RuO₄ by solving Eliashberg equation for three-band Hubbard model, where the effective pairing interaction is expanded perturbatively up to the third order with respect to the Coulomb integrals and the transition temperature is estimated numerically. The most significant momentum dependence of the effective interaction for the spin-triplet p-wave superconductivity does not originate from that of the spin susceptibility, but is brought by the third order vertex corrections. The results show that the p-wave pairing state is stabilized for not so strong inter-orbit couplings.