Enhancement of edge channel transport by a low frequency irradiation
  The magnetotransport properties of high mobility two dimensional electron gas have recently attracted a significant interest due to the discovery of microwave induced zero resistance states. Here we show experimentally that microwave irradiation with a photon energy much smaller than the spacing between Landau levels can induce a strong decrease in the four terminal resistance. This effect is not predicted by the bulk transport models introduced to explain zero resistance states, but can be naturally explained by an edge transport model. This highlights the importance of edge channels for zero resistance state physics that was proposed recently. 
A.D. Chepelianskii, J. Laidet, I. Farrer, H.E. Beere, D.A. Ritchie, H.   Bouchiat
cond-mat.mes-hall