Ferromagnetic Spin Fluctuation Induced Superconductivity in ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$

We propose a quantitative model for triplet superconductivity in ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ based on first principles calculations for the electronic structure and magnetic susceptibility. The superconductivity is due to ferromagnetic spin fluctuations that are strong at small wave vectors. The calculated effective mass renormalization, renormalized susceptibility, and superconducting critical temperature are all in good agreement with experiment. The order parameter is of comparable magnitude on all three sheets of the Fermi surface.