Triplet Pairing Superconductivity Induced by Short-Range Ferromagnetic Correlations in Sr₂RuO₄

抄録

The microscopic origin of triplet superconductivity in Sr₂RuO₄ is discussed, paying attention to the role of Coulomb interaction, U_pp, at the O site. It is shown on the d–p model that U_pp induces a ferromagnetic exchange interaction between “d-electrons” (molecular orbital with d_xy-symmetry) at adjacent Ru sites, leading to short-range ferromagnetic correlations and promoting Cooper pairing with (sinp_x±isinp_y)-symmetry on the γ-band. The reason why such ferromagnetic correlations work effectively may be traced back to the fact that the level of 4d-electrons at Ru sites is relatively low and located near that of 2p-electrons at O sites.