Magnetic field breakdown of electron hydrodynamics

Using spatially and temporally resolved microphotoluminescence, the effect of a strong magnetic field on the hydrodynamic properties of an electron-hole fluid is studied. The recombination rate of photogenerated holes is related to the rate of their diffusion. In this way, the electronic Venturi effect is observed in a mesoscopic variable-width GaAs channel and is used as a tool to probe the hydrodynamic response. It is shown that a quantizing magnetic field leads to the disappearance of the Venturi effect, which means that electron-hole fluid becomes nonhydrodynamic. The observed transition from the hydrodynamic regime to the nonhydrodynamic one is due to the magnetic field-induced decrease in the electron-electron scattering rate and is similar in nature to viscous negative magnetoresistance.