Avoided Antiferromagnetic Order and Quantum Critical Point in CeCoIn$_5$

TL;DR

This study investigates the non-Fermi liquid behavior and quantum criticality in CeCoIn5 near its superconducting critical field, revealing the absence of antiferromagnetic order and suggesting a quantum critical point close to $H_{c2}$.

Contribution

The paper provides experimental evidence that the non-Fermi liquid behavior in CeCoIn5 is due to incipient antiferromagnetism near the quantum critical point, challenging previous assumptions about magnetic order.

Findings

Non-Fermi liquid behavior observed at 5T down to 50mK.

Crossover from Fermi liquid to Non-Fermi Liquid above 8T.

Quantum critical point likely near the superconducting critical field $H_{c2}$.

Abstract

We measured specific heat and resistivity of heavy fermion CeCoIn5 between the superconducting critical field $H_{c2} = 5 T$ and 9 T, with field in the [001] direction, and at temperatures down to 50mK. At 5T the data show Non Fermi Liquid behavior down to the lowest temperatures. At field above 8T the data exhibit crossover from the Fermi liquid to a Non Fermi Liquid behavior. We analyzed the scaling properties of the specific heat, and compared both resistivity and the specific heat with the predictions of a spin-fluctuation theory. Our analysis leads us to suggest that the NFL behavior is due to incipient antiferromagnetism (AF) in CeCoIn5, with the quantum critical point in the vicinity of the $H_{c2}$. Below $H_{c2}$ the AF phase which competes with the paramagnetic ground state is superseded by the superconducting transition.