COLLECTIVE MODES AND SUPERCONDUCTIVITY IN AN EXTENDED HUBBARD-MODEL FOR COPPER-OXIDE SUPERCONDUCTORS

A three-band extended Hubbard model for CuO2 planes is explored within a self-consistent-field approximation. The collective modes for both charge and spin fluctuations are calculated, including leading-order self-energy corrections for the quasiparticle propagators; this leads to an approximate form for the renormalized quasiparticle interactions, used to study superconductive pairing. We find that spin fluctuations promote pairing of B1g symmetry (dx2-y2), and charge fluctuations between Cu and O induce either A1g (extended s) or B2g (dxy) pairing. © 1990 The American Physical Society.