We extend the two-particle self-consistent method proposed by Vilk and Tremblay (J. Phys. I France 7, 1309-1368 (1997)) to study superconductivity in multi-orbital systems. Starting with the sum rules for the spin and charge susceptibilities, we derive self-consistent equations to determine the renormalized effective interactions. We apply this method to the two-orbital dx2−y2-d3z2−r2 model for La2CuO4 and the five-orbital d-model for LaFeAsO. Comparing the results with those of the random phase approximation or the fluctuation exchange approximation in which vertex corrections are ignored, we discuss how the vertex corrections affect the pairing instability of La2CuO4 and the dominant pairing symmetry of LaFeAsO.
@article{arxiv.1301.3254,
title = {Development of a two-particle self-consistent method for multi-orbital systems and its application to unconventional superconductors},
author = {Hideyuki Miyahara and Ryotaro Arita and Hiroaki Ikeda},
journal= {arXiv preprint arXiv:1301.3254},
year = {2013}
}