Orbital superexchange and crystal field simultaneously at play in YVO3: Resonant inelastic x-ray scattering at the VLedge and the OKedge

Abstract

We report on the observation of orbital excitations in YVO${}_{3}$ by means of resonant inelastic x-ray scattering (RIXS) at energies across the vanadium $L$${}_{3}$ and oxygen $K$ absorption edges. At the V $L$${}_{3}$ edge, we are able to resolve the full spectrum of orbital excitations up to 5 eV. In order to unravel the effect of superexchange interactions and the crystal field on the orbital excitations, we analyzed the energy and temperature dependence of the intra-${t}_{2g}$ excitations at 0.1--0.2 eV in detail. While these results suggest a dominant influence of the crystal field, peak shifts of about 13--20 meV observed as a function of the transferred momentum $q\ensuremath{\parallel}a$ reflect a finite dispersion of the orbital excitations. This is puzzling since theoretical models based on superexchange interactions predict a dispersion only for $q\ensuremath{\parallel}c$. Furthermore, we demonstrate that RIXS at the O $K$ edge is very sensitive to intersite excitations. At the O $K$ edge, we observe excitations across the Mott-Hubbard gap and an additional feature at 0.4 eV, which we attribute to two-orbiton scattering, i.e., an exchange of orbitals between adjacent sites. Altogether, our results indicate that both superexchange interactions and the crystal field are important for a quantitative understanding of the orbital excitations in YVO${}_{3}$.