Probing the Kondo Lattice

TL;DR

This paper proposes a phenomenological model for the Kondo lattice in heavy electron superconductor CeCoIn5, describing a crossover from a Kondo gas to a heavy electron liquid with specific heat, susceptibility, and resistivity behaviors.

Contribution

It introduces a new phenomenological framework linking the Kondo gas and heavy electron liquid, with an order parameter based on the condensed fraction, supported by experimental data.

Findings

Partial condensation of Kondo gas into a heavy electron liquid below T*

The Wilson ratio remains constant at 2.0 in the condensed phase

Resistivity is proportional to the non-condensed fraction of Kondo impurities

Abstract

We present a phenomenological solution of the Kondo lattice that is derived from an analysis of the bulk specific heat and spin susceptibility of the heavy electron superconductor CeCoIn5. We find that below a crossover temperature corresponding to the intersite coupling scale, T* ~ 45 K, the Kondo gas (of non-interacting Kondo impurities) partially condenses into a heavy electron "Kondo" liquid that has a temperature independent Wilson ratio = 2.0. The relative fraction, f, of the "condensed" Kondo liquid component plays the role of an order parameter; it increases linearly with decreasing temperature until it saturates at its low temperature value of 0.9. The resistivity is shown to be simply the product of (1-f) and that of an isolated Kondo impurity. The generality of this result is suggested by the corresponding analysis for Ce1-xLaxCoIn5 and CeIrIn5.