On superconducting pairing in the two-band Hubbard model

A two-band Hubbard model for highly hybridized copper 3d(x ²–y ²) and oxygen 2p(x,y) electrons in CuO₂ plane with strong Coulomb repulsion at copper sites is considered. A real-space pairing mechanism induced by antiferromagnetic interaction of Kondo type is treated. To avoid the Gutzwiller approximation the projection technique for two-time Green functions for Hubbard operators is employed. It is shown that due to rigorous restriction of no double occupancy at copper sites the exchange-mediatedp-d pairing with a site-independent gap function isabsent.