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

Abstract

We have probed the magnetic field dependence of the electron phase coherence time $\ddot{I}{„}_{\ddot{I}}•$ by measuring the Aharonov-Bohm conductance oscillations of mesoscopic Cu rings. Whereas $\ddot{I}{„}_{\ddot{I}}•$ 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 $\ddot{I}{„}_{\ddot{I}}•$ at low temperature in weakly disordered metallic thin films is the presence of extremely dilute magnetic impurities.

Accepted for publication in Physical Review Letters