Anomalous Temperature Dependence of the Dephasing Time in Mesoscopic Kondo Wires

We present measurements of the magnetoconductance of long and narrow quasi-one-dimensional gold wires containing magnetic iron impurities in a temperature range extending from 15 mK to 4.2 K. The dephasing rate extracted from the weak antilocalization shows a pronounced plateau in a temperature region of 300–800 mK, associated with the phase breaking due to the Kondo effect. Below the Kondo temperature, the dephasing rate decreases linearly with temperature, in contradiction with standard Fermi-liquid theory. Our data suggest that the formation of a spin glass due to the interactions between the magnetic moments is responsible for the observed anomalous temperature dependence.

Figure 1

Resistivity and phase coherence time as a function of temperature. The sample contains 60 ppm of Fe impurities.

Figure 2

Resistivity and phase coherence time as a function of temperature. The sample contains 15 ppm of Fe impurities.

Figure 3

Dephasing rate in the low temperature range: The straight line is a guide for the eyes. Inset: Dephasing rate over the entire temperature range on a log-log plot.

Figure 4

Dephasing rate in the low temperature range: The straight line is a guide for the eyes. Inset: Dephasing rate over the whole temperature range on a log-log plot.

Figure 5

Magnetic scattering rate for sample A and sample B obtained by subtraction of the standard dephasing rate from the data of the insets of Figs. 3, 4.