Resonant inelastic X-ray scattering of spin-charge excitations in Kondo systems

In cerium compounds, the strong electron-electron interactions of the f states and the hybridization of the f and conduction electrons lead to remarkable magnetic, electronic, and thermodynamic properties at low temperatures featuring heavy fermion behavior, the Kondo effect and intermediate valence [1,2]. Resonant inelastic X-ray scattering (RIXS) has proved to be an efficient tool for the direct characterization of Kondo materials. In addition to the transitions close to the elastic peak (Kondo resonance and spin-orbit satellite), RIXS yields direct access to the f¹-f⁰ and f¹-f² charge excitations as observed in combined photoemission spectroscopy (PES) and inverse PES [3,4].



We will present a RIXS study of the [5] alloy excited at the Ce edge. The observed spectral weight of the fluorescence-like structure decreases dramatically across the - transition and exhibits a hysteresis as a function of temperature. A similar temperature dependence is observed for the final state, which suggests that the fluorescence-like structure is correlated with the weight of the configuration in the ground state and reflects the Kondo scale. The results indicate that the Ce-edge RIXS is a reliable quantitative probe of the electronic structure of strongly correlated Ce-based Kondo systems and is sensitive to the emergent Kondo energy scale. We will also introduce the “PEAXIS” combined spectrometer for carrying out PhotoElectron spectroscopy and RIXS experiments which is in operation at BESSY II.