Microwave-enhanced phase-relaxation observed in weak-localization experiments

Thin magnesium films in a weak localization regime have been studied at low temperatures in an applied microwave field. The effect of amplitude and frequency of the microwaves has been measured. Measurements of the low-field magnetoresistance as a function of microwave power allow us to conclude that the microwaves give rise to a phase-relaxation rate which is independent of and additive to the intrinsic phase-relaxation mechanisms. Our experiments support the theoretical predictions by Altshuler, Aronov, and Khmelnitsky. The change of the dc resistance of our films with microwave power in zero dc magnetic field has also been measured. We find this to be only partly explained by the phase-relaxation rate deduced from the magnetoresistance.