T/B scaling without quasiparticle mass divergence: YbCo2Ge4

TL;DR

This study investigates the non-Fermi liquid behavior of YbCo$_2$Ge$_4$, revealing $T/B$ scaling without evidence of a zero-field quantum critical point, challenging previous interpretations of such scaling.

Contribution

It demonstrates that $T/B$ scaling occurs in YbCo$_2$Ge$_4$ without the presence of a quantum critical point, providing new insights into non-Fermi liquid behavior.

Findings

$T/B$ scaling observed in $ ext{YbCo}_2 ext{Ge}_4$

Electronic heat capacity saturates at low $T$, excluding ferromagnetic quantum criticality

Scaling does not necessarily indicate a quantum critical point

Abstract

YbCo$_2$Ge$_4$ is a clean paramagnetic Kondo lattice which displays non-Fermi liquid behavior. We report a detailed investigation of the specific heat, magnetic Gr\"uneisen parameter ($\Gamma_{\rm mag}$) and temperature derivative of the magnetization ($M$) on a high-quality single crystal at temperatures down to $0.1$~K and magnetic fields up to 7~T. $\Gamma_{\rm mag}$ and $dM/dT$ display a divergence upon cooling and obey $T/B$ scaling. Similar behavior has previously been found in several other Yb-based Kondo lattices and related to a zero-field quantum critical point without fine tuning of pressure or composition. However, in the approach of $B\rightarrow 0$ the electronic heat capacity coefficient of YbCo$_2$Ge$_4$ saturates at low $T$, excluding ferromagnetic quantum criticality. This indicates that $T/B$ scaling is insufficient to prove a zero-field quantum critical point.