SPECTRAL-WEIGHT TRANSFER IN EFFECTIVE SINGLE-BAND MODELS FOR THE HIGH-T(C) CUPRATES

The low-energy physics of the Emery model, representing the high-T(c) cuprates, can be understood by separating intracell interference within CuO4 cells from intercell correlations described by an effective single-band Hubbard model. This decomposition explains the anomalous transfer of spectral intensity from the high- to the low-energy scale, the asymmetry between electron and hole doping, and the breakdown of low-energy sum rules. These features are related to the existence of an antibound charge transfer exciton band, and are very sensitive to the strength of the Coulomb repulsion U(d).