Zero-field Quantum Critical Point in CeCoIn$_5$

TL;DR

This study provides evidence for a zero-field quantum critical point in CeCoIn$_5$ through measurements of magnetic Grüneisen ratio and specific heat, revealing universal scaling and increased quasiparticle entropy near zero field.

Contribution

It demonstrates the existence of a zero-field quantum critical point in CeCoIn$_5$ using thermodynamic measurements and scaling analysis, advancing understanding of quantum criticality in heavy-fermion metals.

Findings

Universal temperature over magnetic field scaling of $mma_H$ in the normal state

Quasiparticle entropy increases as the field approaches zero within the superconducting state

Evidence supports a hidden quantum critical point at zero magnetic field

Abstract

Quantum criticality in the normal and superconducting state of the heavy-fermion metal CeCoIn$_5$ is studied by measurements of the magnetic Gr\"{u}neisen ratio, $\Gamma_H$, and specific heat in different field orientations and temperatures down to 50 mK. Universal temperature over magnetic field scaling of $\Gamma_H$ in the normal state indicates a hidden quantum critical point at zero field. Within the superconducting state the quasiparticle entropy at constant temperature increases upon reducing the field towards zero, providing additional evidence for zero-field quantum criticality.