Pairing symmetry and dominant band in Sr2RuO4

Abstract: We study the superconductivity pairing mechanism in Sr2RuO4 in the limit of small interaction by extending a renormalization group calculation developed by Raghu et al. [Phys. Rev. B 81, 224505 (2010)] to include spin-orbit coupling and multiband effects. We show these effects to be crucial to discriminate between the possible order parameters. In contrast to previous results and without the necessity of fine-tuning, we obtain pseudospin-triplet gaps of the same order of magnitude on the two-dimensional gamma band and the quasi-one-dimensional alpha and beta bands. The ratio of the gap amplitude on the different bands varies continuously with the interaction parameter. The favored pairing symmetry is shown to be chiral when gamma is slightly dominant and helical when alpha and beta are slightly dominant.