Calculations using a realistic multi-band extended Hubbard hamiltonian, which correctly describes the Heisenberg excitation spectrum and superexchange energy of the insulating phase of CuO2, show that the two largest energies relating to the carrier quasiparticle are the carrier bandwidth (> 5 eV) and an exceptionally large (∼3 eV times a density of states factor as in an RKKY interaction) effective exchange energy between a delocalized carrier hole and a localized Cu hole. The Cu holes are found to remain localized in the superconducting materials. Calculations using a model pairing hamiltonian show that this exchange induces (through partial spin-polarization of the Cu holes) an attraction between carriers. This attraction is strong enough to overcome a realistic Coulomb repulsion, hence leading to net attractive pairing. Triplet p-wave (or possibly singlet d-wave) pairing is implied.
ASJC Scopus subject areas
- Condensed Matter Physics