Resolving dd transitions in NaV2O5 using angle-resolved resonant inelastic x-ray scattering at the V L edge -: art. no. 125102

In NaV2O5, the vanadium d(xy) density of states (V-d(xy)) dominates the Fermi surface while the hybridized vanadium d and oxygen p states (V-d/O-p) are located about 6 eV below the Fermi surface. In the resonant inelastic x-ray scattering spectrum, the transition between vanadium d bands leads to a V-dd peak of about -1.5 eV while transitions between vanadium d and oxygen p states lead to a broad V-d/O-p peak at approximately -6 eV. While there is little controversy over the origin of the V-d/O-p peak, the V-dd peak has been assigned to transitions to either the V-d(xy) or the V-d(xz)/d(yz) bands. Here angle-dependent resonant inelastic x-ray scattering at the V-L-3 edge is analyzed to determine the origin of the V-dd peak in NaV2O5. Experiment shows that as the incident photon polarization is rotated from the b to c axis, the V-dd peak grows relative to the V-d/O-p peak and its energy loss becomes larger. Our first-principles calculations demonstrate that such growth must involve both the unoccupied d(xy) and d(xz)/d(yz) bands. Neither the d(xz)/d(yz) nor d(xy) excitation alone can reproduce the ratio change. For the bc scan, the light first samples the d(xy) orbital and then the d(xz)/d(yz) orbital. Slightly detuning the incident energy away from the resonant edge reveals that the d(xy) band is slightly lower in energy and much narrower than the d(xz)/d(yz) band. The results support our previous conclusion that electron correlation splits the d(xy) band and the smallest energy loss is a good measure of the gap between the split bands.