Theory of superconducting mechanism and gap structure of Sr2RuO4

We discuss a possible mechanism of the spin-triplet superconductivity and a gap structure of Sr2RuO4. We calculate transition temperature as a function of the on-site Coulomb energy, and determine the momentum dependences of the superconducting gap, by solving the linearized Eliashberg equation for a realistic three-band Hubbard model. Here the effective pairing interaction is expanded perturbatively with respect to the on-site Coulomb interaction up to the third order. In the present article we display the results of the calculations of transition temperature and specific heat in the superconducting state. We obtain a relatively high transition temperature as a result of the effective interaction favoring p-wave pairing. The theoretical gap structure reproduces the experimental temperature dependence of specific heat very well. (C) 2003 Elsevier Science B.V. All rights reserved.