CHARGE FLUCTUATIONS - SPIN FLUCTUATIONS AND SUPERCONDUCTIVITY IN A CUO2 SHEET

A Ud= Anderson lattice model with a tight-binding band structure is used to model the CuO2 sheets of the high-Tc oxides. The model is treated within a strong-coupling slave-boson method treating spin and charge fluctuations on equal footing. At the mean-field level the normal state is a Fermi liquid at finite doping with a transition to a charge-transfer insulator at half-filling for a large enough charge-transfer gap. Charge fluctuations give rise to a repulsive quasiparticle interaction, but spin fluctuations give rise to an antiferromagnetic exchange interaction and it is shown that this leads to strong-coupling s-wave pairing for physically reasonable values of the charge-transfer gap. © 1990 The American Physical Society.