SELF-CONSISTENT WEAK-COUPLING STUDY OF THE 3-BAND CUO2 MODEL

The ''fluctuation-exchange'' approximation, a Baym-Kadanoff theory use d previously to treat the one-band Hubbard model, is used to investiga te a three-band model for the CuO2 planes in the cuprate superconducto rs. Attention is restricted to (a) nearest-neighbor copper-oxygen hopp ing and (b) a Hubbard-like Coulomb interaction on copper sites only. O rbital-occupancy factors are shown to be in good agreement with previo us quantum simulation studies. An instability eigenvalue analysis conf irms that, as in the one-band model, the most likely channel for super conductivity is a dx2-y2 singlet. The scale for onset of exponentially long-ranged antiferromagnetic correlations is compared with results f or the one-band model, and the role of hybridization in reducing the e ffective Coulomb interaction is studied using a transformation to Wann ier states.