Looking for orbiton dispersion features in GdVO3 with the aim of RIXS

We compute the theoretical RIXS spectra for the dd excitations at the vanadium L3 edge in GdVO3, as a function of energy and momentum transfer, by factorizing the RIXS spectral function into two parts: (i) a single-site part with a core hole present and (ii) a lattice part without the core hole. The obtained results are compared with the direct measurements on the compound for four different angles, carried out with SAXES at the ADDRESS beamline (PSI Villigen, Switzerland). The experimental spectra show a shoulder at low energy with a clearly visible shift corresponding to different momentum transfers. We investigate the possible origin of this shift, in order to distinguish between a crystal field effect (weight transfer between two or more different peaks) and an orbiton dispersion feature predicted by the superexchange mechanism for 3d2 degenerate electrons in V3+ ions.