Microwave induced magnetoresistance oscillations at the subharmonics of the cyclotron resonance

The magnetoresistance oscillations that occur in a two-dimensional electron system exposed to strong microwave radiation when the microwave frequency ω coincides with the nth subharmonic of the cyclotron frequency ω _c have been investigated for n = 2, 3, and 4. It is shown that these subharmonic features can be explained within a nonequilibrium energy distribution function picture without invoking multiphoton absorption processes. The existence of a frequency threshold above which such oscillations disappear lends further support to this explanation.