Resonant inelastic x-ray scattering of spin-charge excitations in a Kondo system

Resonant inelastic x-ray scattering (RIXS) studies across the Ce M5 edge have been carried out to investigate the electronic structure of the ferromagnetic CeAgSb2 Kondo system. The RIXS spectra exhibit energy loss features corresponding to final states usually observed by combining photoemission and inverse photoemission spectroscopy. At low energy loss, a clear signature of the spectral features corresponding to the spin-orbit interaction is also observed. Polarization dependence provides evidence for the 1S0 symmetry singlet ground state by a total suppression of the f0 final state. A simplified single-impurity Anderson model combined with full multiplet theory allows an accurate description of the spin-charge excitations. The RIXS data also reveal a strong temperature T dependence of the fluorescencelike structure. We conjecture that this behavior reflects the T dependence of the Kondo resonance.