Charge and orbital excitations in Li2CuO2

TL;DR

This study uses resonant inelastic x-ray scattering to investigate electronic excitations in Li2CuO2, revealing localized orbital and charge-transfer excitations with minimal momentum dependence, and indicating notable interchain interactions.

Contribution

First detailed RIXS analysis of Li2CuO2 revealing localized and charge-transfer excitations with insights into interchain coupling effects.

Findings

Identified a dispersionless d-d orbital excitation at ~2.1 eV.

Observed charge-transfer excitations at ~5.4 eV and ~7.6 eV.

Detected small energy dispersion perpendicular to copper-oxygen ribbons.

Abstract

We report a resonant inelastic x-ray scattering study of electronic excitations in Li_2CuO_2, 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 ~2.1 eV is dispersionless and is attributed to a localized d-d orbital excitation. We also observe two excitations at ~5.4 eV and ~7.6 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.