Dephasing by extremely dilute magnetic impurities revealed by Aharonov-Bohm oscillations.
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.
Pierre
F
F
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320, USA.
Birge
Norman O
NO