Observation of a node in the quantum oscillations induced by microwave   radiation
  The microwave induced magnetoresistance in GaAs/AlGaAs heterostructure was studied at temperatures below 1K and frequencies in the range of 150-400 GHz. A distinct node in the Shubnikov- de Haas oscillations, induced by the microwave radiation, is clearly observed. The node position coincides with the position of the cyclotron resonance on the carriers with effective mass (0.068 +/- 0.005) m0. 
Alexey E. Kovalev, Sergey A. Zvyagin, Clifford R. Bowers, John L. Reno   and Jerry A. Simmons