Spin-triplet superconductivity due to antiferromagnetic spin-fluctuation in Sr2RuO4

A mechanism leading to the spin-triplet superconductivity is proposed based on the antiferromagnetic spin-fluctuation. The effects of anisotropy in spin-fluctuation on the Cooper pairing and on the direction of d vector are examined in the one-band Hubbard model with random-phase approximation. The gap equations for the anisotropic case are derived and applied to Sr2RuO4. It is found that a nesting property of the Fermi surface together with the anisotropy leads to the triplet superconductivity with the d = &zcirc;(sink(x)+/-isink(y)), which is consistent with experiments.