Dephasing by extremely dilute magnetic impurities revealed by Aharonov-Bohm oscillations

TL;DR

This study investigates how extremely dilute magnetic impurities affect electron phase coherence in mesoscopic copper rings, revealing that magnetic fields can significantly influence dephasing, which explains the low-temperature saturation of coherence time.

Contribution

It provides experimental evidence linking dilute magnetic impurities to dephasing saturation, using Aharonov-Bohm oscillations in mesoscopic rings.

Findings

Magnetic impurities cause dephasing saturation at low temperatures.

Aharonov-Bohm oscillation amplitude increases with magnetic field.

Magnetic field dependence indicates magnetic impurities influence phase coherence.

Abstract

We have probed the magnetic field dependence of the electron phase coherence time $\tau_\phi$ by measuring the Aharonov-Bohm conductance oscillations of mesoscopic Cu rings. Whereas $\tau_\phi$ determined from the low-field magnetoresistance saturates below 1 K, the amplitude of Aharonov-Bohm $h/e$ oscillations increases strongly on a magnetic field scale proportional to the temperature. This provides strong evidence that a likely explanation for the frequently observed saturation of $\tau_\phi$ at low temperature in weakly disordered metallic thin films is the presence of extremely dilute magnetic impurities.