BaVS3 probed by V L edge x-ray absorption spectroscopy

Polarization dependent vanadium L edge x-ray absorption spectra of BaVS(3) single crystals are measured in the four phases of the compound. The difference between signals with the polarizations E perpendicular to c and E is parallel to c (linear dichroism) changes with temperature. Besides increasing the intensity of one of the maxima, a new structure appears in the pre-edge region below the metal-insulator transition. More careful examination brings to light that the changes start already with pretransitional charge density wave fluctuations. Simple symmetry analysis suggests that the effect is related to rearrangements in the E(g) and A(1g) states, and is compatible with the formation of four inequivalent V-sites along the V-S chain.

Probing the transition in bulk Ce under pressure: a direct investigation by resonant inelastic X-ray scattering

We report on the most complete investigation to date of the -electron properties at the transition in elemental Ce by resonant inelastic x-ray scattering (RIXS). The Ce 2p3d-RIXS spectra were measured directly in the bulk material as a function of pressure through the transition. The spectra were simulated within the Anderson impurity model. The occupation number n(f) and f double occupancy were derived from the calculations in both gamma and alpha phases in the ground state. We find that the electronic structure changes result mainly from band formation of 4f electrons which concurs with reduced electron correlation and increased Kondo screening at high pressure.

f-State occupancy at the gamma-alpha phase transition of Ce-Th and Ce-Sc alloys

Resonant inelastic x-ray scattering spectra were measured for a series of Ce solid solutions (Ce-Th and Ce-Sc) across the gamma-alpha phase transition. They reveal a well-defined feature associated with the 4f2 configuration when the incident energy is tuned to the Ce L3 preedge region. This component is normally hidden in x-ray absorption spectra because of lifetime broadening. The f1/f2 ratio estimated by resonant inelastic x-ray scattering presents a sharp drop across the gamma-alpha transition and hysteresis as a function of temperature that closely resemble the magnetization loop. These measurements confirm recent dynamical mean-field theory calculations that unexpectedly predict significant double occupancy of f orbitals in the ground state.