Rotational Gr\"{u}neisen ratio: a probe for quantum criticality in anisotropic systems

TL;DR

This paper introduces the rotational Grüneisen ratio as a new thermodynamic probe for detecting quantum criticality in highly anisotropic magnetic systems, demonstrated through experiments on CeRhSn and CeIrSn.

Contribution

It proposes a novel rotational Grüneisen ratio that uses field orientation as a control parameter to identify quantum critical behavior in anisotropic materials.

Findings

Scaling of $\

the same critical exponents and field-invariant critical field angle.

The scaling function reveals highly anisotropic quantum criticality related to the easy-axis component of the magnetic field.

Abstract

The Gr\"{u}neisen ratio $\Gamma$ and its magnetic analog, the magnetic Gr\"{u}neisen ratio $\Gamma_H$, are powerful probes to study the nature of quantum phase transitions. Here, we propose a Gr\"{u}neisen parameter, the rotational Gr\"{u}neisen ratio $\Gamma_\phi$, by introducing the orientation of the external field as a control parameter. We investigate $\Gamma_\phi$ of the highly anisotropic paramagnets CeRhSn and CeIrSn by measuring the rotational magnetocaloric effect in a wide range of temperatures and magnetic fields. We find that the $\Gamma_\phi$ data of both compounds are scaled by using the same critical exponents and the field-invariant critical field angle. Remarkably, the scaling function for the $\Gamma_\phi$ data reveals the presence of highly anisotropic quantum criticality that develops as a function of the easy-axis component of the magnetic field from the quantum critical line. This paper provides a thermodynamic approach to detect and identify magnetic quantum criticality in highly anisotropic systems.