Frequency-dependent Inter-pseudospin Solutions to Superconducting Strontium Ruthenate

Abstract

The lasting puzzle of the superconducting order parameter of Sr${}_2$RuO${}_4$ calls for theoretical studies that include seldom-considered effects. Here we include spin-orbit coupling effects on the electronic structure and then solve the linearized Eliashberg equation in a pseudospin basis, including the possibility that spin and charge fluctuations induce frequency-dependent superconducting order parameters. We find that spin-orbit coupling mixes even and odd contributions in orbital, spin and frequency spaces and that leading inter-pseudospin symmetries, B${}_{1g}^{+}$ and A${}_{2g}^{-}$, have intra-orbital components respectively even and odd in Matsubara frequency. An accidental degeneracy between these could resolve apparent experimental contradictions.

7 pages, 3 figures. Companion paper submitted separately: arXiv:2201.08918