Superconducting pairing in Sr2RuO4 from weak to intermediate coupling

The unconventional superconductivity in Sr2RuO4 continues to attract considerable interest. Although many measurements can be interpreted on the basis of chiral p-wave pairing with intriguing topological character, a number of exceptions hinder an unambiguous verification of such pairing. The pairing mechanism also remains under debate. In this Rapid Communication, with effects of the sizable spin-orbit coupling accounted for, we reexamine the superconducting instabilities in Sr2RuO4 through systematic microscopic analysis within the random-phase approximation. Our calculations show that the odd-parity p-wave pairing is favored in the regime of extremely weak interactions, but that highly anisotropic even-parity pairings become most leading over a broad range of stronger interactions. These results could shed light on the nature of the enigmatic superconductivity in Sr2RuO4.