Can competition between crystal field and Kondo effect cause non-Fermi liquid like behavior?

TL;DR

This paper investigates how the interplay between crystal field splitting and Kondo effects can lead to non-Fermi liquid-like behavior in Ce-based compounds, emphasizing the importance of a crossover between SU(4) and SU(2) Kondo regimes.

Contribution

It introduces a model considering crystal field splitting and Kondo effects to explain non-Fermi liquid behavior in Ce$_{1-x}$La$_{x}$Ni$_{9}$Ge$_4$, highlighting a crossover between different Kondo regimes.

Findings

Crossover between SU(4) and SU(2) Kondo effects occurs at low temperatures.

Different temperature scales govern the screening of two magnetic doublets.

Experimental temperature range still probes the crossover into a Fermi-liquid fixed point.

Abstract

The recently reported unusual behavior of the static and dynamical magnetic susceptibility as well as the specific heat in Ce$_{1-x}$La$_{x}$Ni$_{9}$Ge$_4$ has raised the question of a possible non-Fermi liquid ground state in this material. We argue that for a consistent physical picture the crystal field splitting of two low lying magnetic doublets of the Ce $4f$-shell must be taken into account. Furthermore, we show that for a splitting of the order of the low temperature scale $T^*$ of the system a crossover behavior between an SU(4) and an SU(2) Kondo effect is found. The screening of the two doublets occurs on different temperature scales leading to a different behavior of the magnetic susceptibility and the specific heat at low temperatures. The experimentally accessible temperature regime down to 50mK still lies in the extended crossover regime into a strong coupling Fermi-liquid fixed point.