Electron Coherence in Mesoscopic Kondo Wires

TL;DR

This study investigates electron phase coherence in mesoscopic gold wires with magnetic impurities, revealing Kondo effect signatures and spin glass behavior affecting coherence times at very low temperatures.

Contribution

It provides experimental evidence of phase coherence behavior influenced by Kondo physics and magnetic interactions in mesoscopic wires, highlighting deviations from Fermi liquid theory.

Findings

Plateau in phase coherence time between 300 mK and 800 mK

Increase in coherence time below Kondo temperature

Saturation of coherence time at very low temperatures

Abstract

We present measurements of the magnetoresistance of long and narrow quasi one-dimensional gold wires containing magnetic iron impurities. The electron phase coherence time extracted from the weak antilocalisation shows a pronounced plateau in a temperature region of 300 mK - 800 mK, associated with the phase breaking due to the Kondo effect. Below the Kondo temperature, the phase coherence time increases, as expected in the framework of Kondo physics. At much lower temperatures, the phase coherence time saturates again, in contradiction with standard Fermi liquid theory. In the same temperature regime, the resistivity curve displays a characteristic maximum at zero magnetic field, associated with the formation of a spin glass state. We argue that the interactions between the magnetic moments are responsible for the low temperature saturation of the phase coherence time.