Four-band extended Hubbard Hamiltonian for the one-dimensional cuprate Sr2CuO3: Distribution of oxygen holes and its relation to strong intersite Coulomb interaction

We have carried out experimental and theoretical studies of the unoccupied electronic structure of Sr2CuO3, which can be regarded as the best realizat ion of a one-dimensional model system containing cuprate chains. In the pol arization-dependent x-ray absorption spectra, the contributions to the uppe r Hubbard band from states originating from the two inequivalent oxygen sit es are energetically well separated. Theoretical analysis of the measured h ole distribution within cluster calculations reveals a markedly enhanced ef fective nearest-neighbor intersite Coulomb interaction, V(pd)similar to2 to 3 eV, or sizable contributions from next-nearest-neighbor interactions, pr ovided a finite on-site energy difference of the two inequivalent oxygen si tes Delta (pp) is taken into account. Including next-nearest-neighbor inter actions, reasonable agreement can be achieved with recent electron energy-l oss spectroscopy data from the same compound. The 2p oxygen orbital analysi s of the unoccupied electronic structure of the single-chain cuprate Sr2CuO 3 reveals strong similarities with that of the double chain compound SrCuO2 .