A magnetic resonance in high-frequency viscosity of two-dimensional electrons

Two-dimensional (2D) electrons in high-quality nanostructures at low temperatures can form a viscous fluid. We develop a theory of high-frequency magnetotransport in such fluid. The time dispersion of viscosity should be taken into account at the frequencies about and above the rate of electron-electron collisions. We show that the shear viscosity coefficients as functions of magnetic field and frequency have the only resonance at the frequency equal to the doubled cyclotron frequency. We demonstrate that such resonance manifests itself in the plasmon damping. Apparently, the predicted resonance is also responsible for the peaks and features in photoresistance and photovoltage, recently observed on the best-quality GaAs quantum wells. The last fact should considered as an important evidence of forming a viscous electron fluid in such structures.