Charge and orbital excitations in Li2CuO2

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Kim YJ, Hill JP, Chou FC, Casa D, Gog T, Venkataraman CT

Abstract:
We report a resonant inelastic x-ray scattering study of electronic excitations in Li2CuO2, an insulating compound comprised of ribbons of edge-sharing copper-oxygen chains. Three excitations, which show little dependence on momentum transfer, are observed in our measurements. The lowest-energy excitation at similar to2.1 eV is dispersionless and is attributed to a localized d-d orbital excitation. We also observe two excitations at similar to5.4 eV and similar to7.6 eV which we assign to charge-transfer excitations. These high-energy excitations are also dispersionless along the copper-oxygen chain direction. However, in each case we observe a small energy dispersion along the direction perpendicular to the copper-oxygen ribbons, suggesting a significant interchain coupling in this system. We also discuss the possible implications of ferromagnetic nearest-neighbor intrachain coupling on the charge excitation spectra.