T/B scaling without quasiparticle mass divergence: YbCo2Ge4

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 Grüneisen parameter (${\Gamma }_{\mathrm{mag}}$) 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. ${\Gamma }_{\mathrm{mag}}$ 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 $B\to 0$ 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.

6 pages, 6 figures (including supplemental material)

References in corpus (5)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• Quantum critical state in a magnetic quasicrystal
• Quantum Valence Criticality as Origin of Unconventional Critical Phenomena
• Divergence of the Magnetic Grüneisen Ratio at the Field-Induced Quantum Critical Point in YbRh${}_2$Si${}_2$
• Characteristic signatures of quantum criticality driven by geometrical frustration