Importance of conduction electron correlation in a Kondo lattice, Ce2CoSi3

TL;DR

This study reveals that electron correlations among conduction electrons significantly influence the electronic structure of the Kondo lattice compound Ce$_2$CoSi$_3$, emphasizing the need to consider these correlations for accurate modeling.

Contribution

It demonstrates the importance of including electron-electron Coulomb repulsion among conduction electrons in theoretical descriptions of Kondo systems.

Findings

Ce 4f states show Kondo resonance at the Fermi level

Co 3d electrons contribute significantly to conduction band

LDA+U improves agreement with experimental data

Abstract

Kondo systems are usually described by the interaction of strong correlation induced local moment with the highly itinerant conduction electrons. Here, we study the role of electron correlations among conduction electrons in the electronic structure of a Kondo lattice compound, Ce$_2$CoSi$_3$, using high resolution photoemission spectroscopy and {\it ab initio} band structure calculations, where Co 3$d$ electrons contribute in the conduction band. High energy resolution employed in the measurements helped to reveal signature of Ce 4$f$ states derived Kondo resonance feature at the Fermi level and dominance of Co 3$d$ contributions at higher binding energies in the conduction band. The line shape of the experimental Co 3$d$ band is found to be significantly different from that obtained from the band structure calculations within the local density approximations, LDA. Consideration of electron-electron Coulomb repulsion, $U$ among Co 3$d$ electrons within the LDA+$U$ method leads to a better representation of experimental results. Signature of electron correlation induced satellite feature is also observed in the Co 2$p$ core level spectrum. These results clearly demonstrate the importance of the electron correlation among conduction electrons in deriving the microscopic description of such Kondo systems.