Giant off-resonance resistance spike related phenomena in irradiated ultraclean two-dimensional electron systems

We report on theoretical studies of a recently discovered strong radiation-induced magnetoresistance spike obtained in ultraclean two-dimensional electron systems at low temperatures. The most striking feature of this spike is that it shows up on the second harmonic of the cyclotron resonance and with an amplitude that can reach an order of magnitude larger than the radiation-induced resistance oscillations. We apply the radiation-driven electron orbits model in the ultraclean scenario. Accordingly, we calculate the elastic scattering rate (charged impurity) which will define the unexpected resonance spike position. We also obtain the inelastic scattering rate (phonon damping), that will be responsible of the large spike amplitude. We present a microscopical model to explain the dependence of the Landau level width on the magnetic field for ultraclean samples. We find that this dependence explains the experimental shift of the resistance oscillations with respect to the magnetic field found in this kind of samples. We study also recent results on the influence of an in-plane magnetic field on the spike. We are able to reconcile the obtained different experimental response of both spike and resistance oscillations versus an increasing in-plane field. The same model on the variation of the LL width, allows us to explain such surprising results based in the increasing disorder in the sample caused by the in-planed magnetic field. Calculated results are in good agreement with experiments. These results would be of special interest in nanophotonics; they could lead to the design of novel ultrasensitive microwave detectors.