Scaling in the Emergent Behavior of Heavy Electron Materials

TL;DR

This paper explains the NMR Knight shift anomaly in heavy electron materials through hyperfine interactions, revealing a universal behavior below a characteristic temperature T* that signifies the emergence of a heavy electron state.

Contribution

It introduces a new understanding of the Knight shift anomaly by linking it to a correlated Kondo temperature and supports the two-fluid model of heavy electron systems.

Findings

The Knight shift anomaly occurs below T* where a heavy electron component develops.

The heavy electron component scales universally across Ce, Yb, and U materials.

T* is a correlated Kondo temperature indicating intersite coupling strength.

Abstract

We show that the NMR Knight shift anomaly exhibited by a large number of heavy electron materials can be understood in terms of the different hyperfine couplings of probe nuclei to localized spins and to conduction electrons. The onset of the anomaly is at a temperature T*, below which an itinerant component of the magnetic susceptibility develops. This second component characterizes the polarization of the conduction electrons by the local moments and is a signature of the emerging heavy electron state. The heavy electron component grows as log T below T*, and scales universally for all measured Ce, Yb and U based materials. Our results suggest that T* is not related to the single ion Kondo temperature, T_K, but rather represents a correlated Kondo temperature that provides a measure of the strength of the intersite coupling between the local moments. Our analysis strongly supports the two-fluid description of heavy electron materials developed by Nakatsuji, Pines and Fisk.