Detailed Investigation of Gap Structure and Specific Heat in the p-wave Superconductor Sr₂RuO₄

Abstract

We present the highly anisotropic p-wave superconducting gap structure of Sr₂RuO₄, which was determined microscopically by solving the linearized Éliashberg equation on the basis of the perturbation theory with respect to the Coulomb energy at Ru sites. We trace the evolution of the gap function below T_c, following the elementary BCS theory, and calculate specific heat for the superconducting state with the symmetry represented by d(k) ∼ (k_x+ i k_y)ˆz. The strong momentum dependences of the gap structure provide a line-node-like power-law behavior of the specific heat even at extremely low temperature. As a result, the calculation results of specific heat agree with the experimental results well for moderately strong inter-orbit couplings.