Measurement of Aharonov-Bohm oscillations in mesoscopic metallic rings in the presence of a high-frequency electromagnetic field

We report measurements of Aharonov-Bohm oscillations in normal metal rings in the presence of highfrequency electromagnetic fields. The power dependence of the decoherence time scale P agrees well with the anticipated power law P −1/5 when the field-induced decoherence rate ac −1 is large compared to the intrinsic decoherence rate o , measured in the absence of external fields. As theoretically expected, we observe a decline in field-induced decoherence when ac −1 o . The frequency dependence of shows a minimum in the oscillation amplitude at a characteristic frequency ac 1 / o, where o is evaluated from the oscillation amplitude using the standard mesoscopic theory. Both the suppression in the oscillation amplitude and the concomitant change in conductivity allow a direct measurement of the intrinsic decoherence time scale.