Superconducting order of Sr_{2}RuO_{4} from a three-dimensional microscopic model

Abstract

We compute and compare even- and odd-parity superconducting order parameters of strontium ruthenate (Sr_{2}RuO_{4}) in the limit of weak interactions, resulting from a fully microscopic three-dimensional model including spin-orbit coupling. We find that odd-parity helical and even-parity d-wave order are favored for smaller and larger values of the Hund's coupling parameter J, respectively. Both orders are found compatible with specific heat data and the recently reported nuclear magnetic resonance (NMR) Knight shift drop [A. Pustogow et al., Nature 574, 72 (2019)10.1038/s41586-019-1596-2]. The chiral p-wave order, numerically very competitive with helical order, sharply conflicts with the NMR experiment.