Circular polarization dependent study of the microwave photoconductivity   in a two-dimensional electron system
  The polarization dependence of the low field microwave photoconductivity and absorption of a two-dimensional electron system has been investigated in a quasi-optical setup in which linear and any circular polarization can be produced in-situ. The microwave induced resistance oscillations and the zero resistance regions are notedly immune to the sense of circular polarization. This observation is discrepant with a number of proposed theories. Deviations only occur near the cyclotron resonance absorption where an unprecedented large resistance response is observed. 
J. H. Smet, B. Gorshunov, C. Jiang, L. Pfeiffer, K. West, V. Umanksy,   M. Dressel, R. Meisels, F. Kuchar, K. von Klitzing