Scaling of the low temperature dephasing rate in Kondo systems

TL;DR

This study investigates how the dephasing rate in Ag wires with Fe Kondo impurities varies with temperature, revealing universal behavior above 0.1 T_K and deviations at lower temperatures, providing insights into Kondo physics.

Contribution

It demonstrates the universal scaling of the magnetic dephasing rate with temperature over Kondo temperature and compares experimental results with theoretical models for different impurity spins.

Findings

Dephasing rate follows a universal curve when scaled by T_K.

Agreement with theory for T > 0.1 T_K.

Deviations from theory observed at lower temperatures.

Abstract

We present phase coherence time measurements in quasi-one-dimensional Ag wires doped with Fe Kondo impurities of different concentrations $n_s$. Due to the relatively high Kondo temperature $T_{K}\approx 4.3K$ of this system, we are able to explore a temperature range from above $T_{K}$ down to below $0.01 T_{K}$. We show that the magnetic contribution to the dephasing rate $\gamma_m$ per impurity is described by a single, universal curve when plotted as a function of $(T/T_K)$. For $T>0.1 T_K$, the dephasing rate is remarkably well described by recent numerical results for spin $S=1/2$ impurities. At lower temperature, we observe deviations from this theory. Based on a comparison with theoretical calculations for $S>1/2$, we discuss possible explanations for the observed deviations.