Highly correlated two-dimensional viscous electron fluid in moderate magnetic fields

Magnetotransport phenomena often provide critically important information about two-dimensional (2D) electron systems. For example, the independence of magnetophotoresistance of 2D electrons in best-quality quantum wells on the polarization helicity of incident radio-frequency radiation has been treated as a puzzling effect, which is important for characterization of these systems, but had no well-established explanation up to now. Here we develop a phenomenological model of dynamics of a highly correlated 2D electron fluid in moderate magnetic fields, in which shear viscosity and the memory effects in interparticle interaction are crucial. In this system, successive collisions of electrons joined in pairs (that is, the pair correlations in time) turn out to be as important as uncorrelated collisions of statistically independent electrons. The resulting photoresistance exhibits an irregular shape of magneto-oscillations, the absence of the dependence on the helicity of the circular polarization of radiation, and a giant peak near the doubled cyclotron frequency. All these effects were observed in experiments on best-quality GaAs quantum wells in moderate magnetic fields at low temperatures. Although the most general conditions of applicability of the developed phenomenological model are not fully clarified now, this coincidence can point out that 2D electrons in such systems form the highly correlated viscous fluid.