Pressure Dependent Electronic Structure in CeRh$_6$Ge$_4$

TL;DR

This study uses advanced theoretical methods to explore how pressure influences the electronic structure of CeRh$_6$Ge$_4$, revealing a transition from localized to itinerant electron states and identifying a potential quantum critical point.

Contribution

The paper provides a systematic pressure-dependent analysis of CeRh$_6$Ge$_4$'s electronic structure using dynamical mean-field theory combined with density functional theory, highlighting the evolution of electron localization and hybridization.

Findings

Ce-4$f$ electrons are localized at -3.9 GPa and -8.3 GPa, itinerant at 6.5 GPa and 13.1 GPa.

A local quantum critical point is indicated around 0.8 GPa where Kondo screening vanishes.

The Fermi surface changes from 8 sheets to 6 sheets across the transition.

Abstract

Using the state-of-art dynamical mean-field theory combined with density functional theory method, we have performed systematic study on the temperature and pressure dependent electronic structure of ferromagnetic quantum critical material candidate CeRh$_6$Ge$_4$. At -3.9 GPa and -8.3 GPa, the Ce-4$f$ occupation variation, the local magnetic susceptibility, and the low-frequency electronic self-energy behaviors suggest the Ce-4$f$ electrons are in the localized state; whereas at 6.5 GPa and 13.1 GPa, these quantities indicate the Ce-4$f$ electrons are in the itinerant state. The characteristic temperatures associated with the coherent Kondo screening is gradually suppressed to 0 around 0.8 GPa upon releasing external pressure, indicative of a local quantum critical point. Interestingly, the momentum-resolved spectrum function shows that even at the localized state side, highly anisotropic $\mathbf{k}$-dependent hybridization between Ce-4$f$ and conduction electrons is still present along $\Gamma$-A, causing hybridization gap in between. The calculations predict 8 Fermi surface sheets at the local-moment side and 6 sheets at the Kondo coherent state. Finally, the self-energy at 0.8 GPa can be well fitted by marginal Fermi-liquid form, giving rise to a linearly temperature dependent resistivity.