Degeneracy between even- and odd-parity superconductivity in the quasi-one-dimensional Hubbard model and implications for Sr2RuO4

Based on a weak coupling calculation, we show that an accidental degeneracy appears between even- and odd-parity superconductivity in the quasi-one-dimensional (1D) limit of the repulsive Hubbard model on the square lattice. We propose that this effect could be at play on the quasi-1D orbitals Ru ${d}_zx$ and ${d}_zy$ of ${\text{Sr}}₂{\text{RuO}}₄$, leading to a gap of the form ${\mathrm{\ensuremath{\Delta}}}_{\text{even}}+i{\mathrm{\ensuremath{\Delta}}}_{\text{odd}}$ which could help reconcile several experimental results.