Scaling of the Low-Temperature Dephasing Rate in Kondo Systems

We present phase coherence time measurements in quasi-one-dimensional Ag wires doped with Fe Kondo impurities of different concentrations nₛ. Because of the relatively high Kondo temperature TK approximately 4.3 K of this system, we are able to explore a temperature range from above TK down to below 0.01TK. We show that the magnetic contribution to the dephasing rate gammaₘ per impurity is described by a single, universal curve when plotted as a function of T/TK. For T>0.1TK, 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.