Fermi Surface Variation of Ce 4f-electrons in Hybridization Controlled Heavy-Fermion Systems

TL;DR

This study investigates how the Fermi surface topology of Ce 4f-electrons in heavy-fermion systems changes with hybridization strength, revealing size differences linked to electron correlations and Kondo effects.

Contribution

It provides direct experimental evidence of Fermi surface evolution in Ce-based heavy-fermion compounds as a function of hybridization strength, highlighting the role of strong correlations.

Findings

Ce 4f-Fermi surface size decreases with increased hybridization

LDA calculations do not fully explain Fermi surface variation

Fermi surface changes are related to Kondo peak behavior

Abstract

Ce 3d-4f resonant angle-resolved photoemission measurements on CeCoGe$_{1.2}$Si$_{0.8}$ and CeCoSi$_{2}$ have been performed to understand the Fermi surface topology as a function of hybridization strength between Ce 4$f$- and conduction electrons in heavy-fermion systems. We directly observe that the hole-like Ce 4$f$-Fermi surfaces of CeCoSi$_{2}$ is smaller than that of CeCoGe$_{1.2}$Si$_{0.8}$, indicating the evolution of the Ce 4$f$-Fermi surface with the increase of the hybridization strength. In comparision with LDA calculation, the Fermi surface variation cannot be understood even though the overall electronic structure are roughly explained, indicating the importance of strong correlation effects. We also discuss the relation between the Ce 4$f$-Fermi surface variation and the Kondo peaks.