Hydrodynamic charge transport in an GaAs/AlGaAs ultrahigh-mobility two-dimensional electron gas

Viscous fluid in an ultrahigh-mobility two-dimensional electron gas (2DEG) in GaAs/AlGaAs quantum wells is systematically studied through measurements of negative magnetoresistance (NMR) and photoresistance under microwave radiation, and the data are analyzed according to recent theoretical work [P. S. Alekseev, Phys. Rev. Lett. 117, 166601 (2016)10.1103/PhysRevLett.117.166601]. Size-dependent and temperature dependent NMR are found to conform to the theoretical predictions. The size dependence of microwave induced resistance oscillations and that of the second harmonic peak indicate that 2DEG in a moderate magnetic field should be regarded as viscous fluid as well. Size-dependent radiation heating effect is found by using NMR as electron thermometry. Our results suggest that the hydrodynamic effects must be considered in order to understand semiclassical electronic transport in a clean 2DEG.