Gr\"uneisen parameter studies on heavy fermion quantum criticality

TL;DR

This review discusses how the Gr"uneisen parameter and magnetocaloric effect diverge near quantum critical points in heavy-fermion metals, highlighting their theoretical understanding and potential for low-temperature cooling applications.

Contribution

It provides a comprehensive comparison of experimental data with theoretical models on the divergence of the Gr"uneisen parameter in heavy-fermion systems near quantum criticality.

Findings

Divergence of the Gr"uneisen parameter observed near quantum critical points.

Theoretical models including geometrical frustration explain experimental results.

Materials with divergent magnetic Gr"uneisen parameter could enable ultra-low temperature cooling.

Abstract

The Gr\"uneisen parameter, experimentally determined from the ratio of thermal expansion to specific heat, quantifies the pressure dependence of characteristic energy scales of matter. It is highly enhanced for Kondo lattice systems, whose properties strongly dependent on the pressure sensitive antiferromagnetic exchange interaction between f- and conduction electrons. In this review, we focus on the divergence of the Gr\"uneisen parameter and its magnetic analogue, the adiabatic magnetocaloric effect, for heavy-fermion metals near quantum critical points. We compare experimental results with current theoretical models, including the effect of strong geometrical frustration. We also discuss the possibility to use materials with divergent magnetic Gr\"uneisen parameter for adiabatic demagnetization cooling to very low temperatures.