Zhang-Rice singlet-state formation by oxygen1sresonant x-ray emission in edge-sharing copper-oxide systems

Resonant behavior of O $1s$ x-ray emission spectrum (XES) in Cu-based oxides, such as ${\mathrm{CuGeO}}_3$ and ${\mathrm{Li}}_2{\mathrm{CuO}}_2,$ is investigated through the model calculations using an edge-sharing ${\mathrm{Cu}}_2{\mathrm{O}}_6$ cluster. It is shown that the inelastic peaks that originate from the Cu $d-d$ excitations and the Zhang-Rice singlet excitation can be observed on resonance, which indicates the importance of the many-body effects in discussing the O $1s$ resonant XES. It is shown that the Zhang-Rice singlet state can be excited in the O $1s$ XES final state when the Cu spins configuration around the irradiated O site is antiferromagnetic. Therefore the experiment at low temperatures is highly desired.