Zero-resistance States Induced by Bichromatic Microwaves
  We have studied the bichromatic photoresistance states of a two dimensional electron gas in the regime of microwave induced resistance oscillations. Zudov and coworkers found clear experimental evidence of zero-resistance states by measuring the bichromatic resistance in a bidimensional gas of electrons. They found that the bichromatic resistance closely replicates the superposition of the two monochromatic components provided that both contributions are positive. However, the superposition principle is no longer valid if one of the two contributions give rice to a zero-resistance state. The experiments by Zudov and coworkers confirm that negative resistance states are rapidly driven into zero-resistance states through A. V. Andreev's symmetry breaking. In this work we present a model for the bichromatic-photoconductivity of a two dimensional electron system subjected to a uniform magnetic field. Our model includes both components of the microwave radiation, a uniform magnetic field and impurity scattering effects. The conductivity is calculated from a Kubo-like formula. Our calculations reproduce the main features of Zudov's experimental results. 
Alejandro Kunold, Manuel Torres