Low Frequency Spin Dynamics in the CeMIn_5 Materials

TL;DR

This study investigates low frequency spin dynamics in CeMIn_5 materials using NMR relaxation measurements, revealing a crossover from Kondo gas to Kondo liquid behavior and providing evidence for quantum criticality in CeCoIn_5.

Contribution

It offers the first detailed analysis of the spin dynamics crossover in CeMIn_5, linking microscopic spin behavior to quantum critical phenomena.

Findings

Identification of a crossover temperature T* separating two spin dynamic regimes.

Evidence of quantum criticality in CeCoIn_5 from spin relaxation data.

Both antiferromagnetic and superconducting states emerge from the Kondo liquid regime.

Abstract

We measure the spin lattice relaxation of the In(1) nuclei in the CeMIn_5 materials, extract quantitative information about the low energy spin dynamics of the lattice of Ce moments in both CeRhIn_5 and CeCoIn_5, and identify a crossover in the normal state. Above a temperature T* the Ce lattice exhibits "Kondo gas" behavior characterized by local fluctuations of independently screened moments; below T* both systems exhibit a "Kondo liquid" regime in which interactions between the local moments contribute to the spin dynamics. Both the antiferromagnetic and superconducting ground states in these systems emerge from the "Kondo liquid" regime. Our analysis provides strong evidence for quantum criticality in CeCoIn_5.