Anisotropic c-f hybridization in the ferromagnetic quantum critical metal CeRh$_6$Ge$_4$

TL;DR

This study uses angle-resolved photoemission to reveal anisotropic hybridization between conduction and 4f electrons in CeRh6Ge4, shedding light on its role in ferromagnetic quantum criticality.

Contribution

It provides the first spectroscopic evidence of momentum-dependent hybridization anisotropy in CeRh6Ge4, linking electronic structure to quantum critical behavior.

Findings

Hybridization is stronger along the Ce chain direction.

4f bands are momentum-dependent and persist at high temperatures.

Band-dependent evolution of hybridized states observed.

Abstract

Heavy fermion compounds exhibiting a ferromagnetic quantum critical point have attracted considerable interest. Common to two known cases, i.e., CeRh$_6$Ge$_4$ and YbNi$_4$P$_2$, is that the 4f moments reside along chains with a large inter-chain distance, exhibiting strong magnetic anisotropy that was proposed to be vital for the ferromagnetic quantum criticality. Here we report an angle-resolved photoemission study on CeRh6Ge4, where we observe sharp momentum-dependent 4f bands and clear bending of the conduction bands near the Fermi level, indicating considerable hybridization between conduction and 4f electrons. The extracted hybridization strength is anisotropic in momentum space and is obviously stronger along the Ce chain direction. The hybridized 4f bands persist up to high temperatures, and the evolution of their intensity shows clear band dependence. Our results provide spectroscopic evidence for anisotropic hybridization between conduction and 4f electrons in CeRh$_6$Ge$_4$, which could be important for understanding the electronic origin of the ferromagnetic quantum criticality.