Electronic structure of semiconducting CeFe4P12: Strong hybridization and relevance of single-impurity Anderson model

Semiconducting skutterudite $\mathrm{Ce}{\mathrm{Fe}}_{4}{\mathrm{P}}_{12}$ is investigated by synchrotron x-ray photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). $\mathrm{Ce}\phantom{\rule{0.2em}{0ex}}3d$ core-level PES and $3d\text{\ensuremath{-}}4f$ XAS, in combination with single-impurity Anderson model (SIAM) calculations, confirm features due to ${f}^{0}$, ${f}^{1}$, and ${f}^{2}$ configurations. The $\mathrm{Ce}\phantom{\rule{0.2em}{0ex}}3d\text{\ensuremath{-}}4f$ resonant-PES spectra provide the $\mathrm{Ce}\phantom{\rule{0.2em}{0ex}}4f$ density of states (DOS), which indicates the absence of a Kondo resonance at the Fermi level, but can still be explained by SIAM with a small gap in non-$f$ DOS. While $\mathrm{Ce}\phantom{\rule{0.2em}{0ex}}4f$ partial DOS from band structure calculations is consistent with the main $\mathrm{Ce}\phantom{\rule{0.2em}{0ex}}4f$ DOS, the importance of SIAM for core-level PES and XAS spectra quantifies the mixed valence for semiconducting $\mathrm{Ce}{\mathrm{Fe}}_{4}{\mathrm{P}}_{12}$, derived from strong hybridization between non-$f$ conduction and $\mathrm{Ce}\phantom{\rule{0.2em}{0ex}}4f$ DOS.