Crystalline electric field effects in Ce 3$d$ core-level spectra of heavy-fermion systems: Hard X-ray photoemission spectroscopy on CeNi$_{1-x}$Co$_x$Ge$_2$

TL;DR

This study uses high-resolution hard X-ray photoemission to analyze how crystalline electric field effects influence Ce 3d core-level spectra in CeNi$_{1-x}$Co$_x$Ge$_2$, revealing changes in electronic structure and hybridization with Co doping.

Contribution

It demonstrates the impact of crystalline electric field effects on Ce 3d core-level spectra and correlates spectral features with hybridization strength and degeneracy of f-states.

Findings

Satellite structures indicate increasing hybridization with Co concentration.

Multiplet structures of f^1 peaks vary systematically with degeneracy.

Crystalline electric field effects influence core-level spectral features.

Abstract

High-resolution hard X-ray photoemission measurements have been performed to clarify the electronic structure originating from the strong correlation between electrons in bulk Ce 3$d$ core-level spectra of CeNi$_{1-x}$Co$_x$Ge$_2$ (0 $\leq$ $x$ $\leq$ 1). In the Ce 3$d_{5/2}$ core-level spectra, the variation of satellite structures ($f^2$ peaks) shows that the hybridization strength between Ce 4$f$- and conduction electrons gradually increases with Co concentration in good agreement with the results of Ce 3$d-4f$ and 4$d-4f$ resonant photoemission spectroscopies. Particularly, in Ce 3$d_{3/2}$ core-level spectra, the multiplet structures of $f^1$ peaks systematically change with the degeneracy of $f$-states which originates from crystalline electric field effects.