Theory of microwave-induced photocurrent and photovoltage magneto-oscillations in a spatially nonuniform two-dimensional electron gas

Recent experiment (S. I. Dorozhkin et al., Phys. Rev. Lett. 102, 036602 (2009)] on quantum Hall structures with strongly asymmetric contact configuration discovered microwave-induced photocurrent and photovoltage magneto-oscillations in the absence of dc driving. We show that in an irradiated sample the Landau quantization leads to violation of the Einstein relation between the dc conductivity and diffusion coefficient. Then, in the presence of a built-in electric field in a sample, the microwave illumination causes photogalvanic signals which oscillate as a function of magnetic field with the period determined by the ratio of the microwave frequency to the cyclotron frequency, as observed in the experiment.