The frequency dependence of microwave-induced resistance oscillations (MIROs) has been studied experimentally in high-mobility electron $\mathrm{Ga}\mathrm{As}∕\mathrm{Al}\mathrm{Ga}\mathrm{As}$ structures to explore the limits at which these oscillations can be observed. It is found that in dc transport experiments at frequencies above $120\mathrm{GHz}$, MIROs start to quench, while above $230\mathrm{GHz}$, they completely disappear. The results will need to be understood theoretically but are qualitatively discussed within a model in which forced electronic charge oscillations (plasmons) play an intermediate role in the interaction process between the radiation and the single-particle electron excitations between Landau levels.

• Received 8 June 2007

DOI:https://doi.org/10.1103/PhysRevB.76.165321