Experimental investigation of the ratchet effect in a two-dimensional   electron system with broken spatial inversion symmetry
  We report on experimental evidence of directed electron transport, induced by external linear-polarized microwave irradiation, in a two-dimensional spatially-periodic asymmetrical system called ratchet. The broken spatial symmetry was introduced in a high mobility two-dimensional electron gas based on AlGaAs/GaAs heterojunction, by patterning an array of artificial semi-discs-shaped antidots. We show that the direction of the transport is efficiently changed by microwave polarization. The dependence of the effect on magnetic field and temperature is investigated. This represents a significant step towards the realization of new microwave detectors and current generators. 
S. Sassine, Yu. Krupko, J.-C. Portal, Z. D. Kvon, R. Murali, K. P.   Martin, G. Hill, A. D. Wieck