Anderson Hamiltonian description of the experimental electronic structure and magnetic interactions of copper oxide superconductors

Abstract

We describe valence-band and core-level photoemission data for copper oxide superconductors using the Anderson Hamiltonian applied to an impurity-cluster configuration-interaction model. We obtain experimental values of the parameters of the model, the copper⇄oxygen chargetransfer energy Δ∼0.4 eV, the d−d Coulomb interaction U∼6 eV, and the ligand-d hybridization T∼2.4 eV. Using these parameters, we evaluate the linear Cu-O-Cu superexchange interaction J and find it is dominated by the charge-transfer fluctuations. The magnitude obtained for J is much larger than typical Néel temperatures of these materials, and is somewhat larger than that estimated from applying the resonating-valence-bond picture to La2CuO4. We point out that for Δ≪U and T≫Δ the charge-transfer degrees of freedom, and the lattice aspects of the Anderson lattice Hamiltonian, should not be neglected in constructing models for the high-Tc superconductivity. We also emphasize our resonant-photoemission result that the very small density of states at or near the Fermi level in all these materials has a substantial contribution from Cu 3d states, suggesting their importance for the superconductivity. We report other details of the resonant-photoemission data involving La and Ba states in the materials containing these elements.

Source-reported materials — not catalogue approval

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