Toward the Thorough Microscopic Clarification of Superconducting Mechanism and Gap Structure in Sr2RuO4

Abstract

A microscopic mechanism of triplet superconductivity and a possible superconducting gap structure in Sr2RuO4 are discussed on the basis of the standard Fermi liquid picture. We describe the Ru4d‐electron system on the RuO2 networks by using a three‐band repulsive Hubbard model. Many‐electron correlation is treated within the third order perturbation expansion in the on‐site Coulomb interaction. The Eliashberg equation is solved numerically using the effective pairing interaction evaluated perturbatively. As a consequence, a highly anisotropic p‐wave pairing state is obtained as the most probable pairing symmetry. The temperature dependences of specific heat, thermal conductivity and ultrasound attenuation rate are also analyzed, using the band‐ and momentum‐dependent superconducting gap function calculated microscopically. It is shown that the theoretical results are consistent with the temperature dependences of those quantities, assuming the chiral pairing symmetry (i.e., Δ(k) ∼ kx ± iky).