Hydrodynamic electron flow in 2D semiconductor heterostructures*

We propose simple geometries to directly test hydrodynamic flow in 2D electron systems by longitudinal resistance measurements. We model the boundaries of the electron fluid as `slippery', i.e. supporting no longitudinal stress, hence, we show that the viscous component of resistance depends significantly on the geometric features while it vanishes along the straight featureless sections. Moreover, since the viscous resistance increases quadratically with the inverse scale of the system, we show that channels in which the viscous and Ohmic effects are comparable can be manufactured with current technology. Elementary, bent or nozzle/diffuser type channels show significant departure from their diffusive counterparts in the hydrodynamic regime.