Magnetoplasmon resonance in 2D electron system driven into a   zero-resistance state
  We report on a remarkably strong, and a rather sharp, photoresistance peak originating from a dimensional magnetoplasmon resonance (MPR) in a high mobility GaAs/AlGaAs quantum well driven by microwave radiation into a zero-resistance state (ZRS). The analysis of the MPR signalreveals a negative background providing experimental evidence for the concept of absolute negative resistance associated with the ZRS. When a system is further subject to a dc field, the maxima of microwave-induced resistance oscillations decay away and a system reveals a state with close-to-zero differential resistance. The MPR peak, on the other hand, remains essentially unchanged, indicating surprisingly robust Ohmic behavior under the MPR conditions. 
A. T. Hatke, M. A. Zudov, J. D. Watson, and M. J. Manfra
cond-mat.mes-hall