A Two-Band Hubbard Model for Clusters of Doped Copper Oxides and Other Metal Oxides: Populations of Holes and Spin Densities by the Full VB CI Method

Abstract

The two-band Hubbard model for clusters of doped transition metal oxides is solved by the valence-bond (VB) full CI technique. It is found that the holes are mainly introduced upon oxygen sites of doped copper oxides, whereas they are localized on metal sites in the case of the Mott-Hubbard insulators such as iron and manganese oxides. The full VB Cl calculations indicate the important roles of both spin-flip (bitriplet) and spin-unflip (charge-transfer) excitations, which are responsible for electronic fluctuations (correlations) within doped copper oxides. Implications of these results are discussed in relation to the high- T c superccnductivity.