Hydrodynamic effects of ballistic electron jets in high-mobility GaAs/AlGaAs*

The influence of a ballistic electron jet, injected through a lithographic aperture,
is experimentally investigated through nonlocal resistance measurements over a distance L
from the injection point, in a 2D electron system in a high-mobility GaAs/AlGaAs
heterostructure over a temperature range 4 K < T < 40 K, at zero magnetic field. The geometry
consists of various mesoscopic apertures separated by L ranging from 1.3 μm to 20.5 μm such
that the jet can be injected from any aperture and the nonlocal potential induced by the
current distribution can be measured at any other aperture. The measured nonlocal resistance
exhibits a non-monotonic behavior as T is increased, leading to negative values (up to L = 12.8
μm) in an intermediate T range. This T range lies in the hydrodynamic regime of transport
where electron-electron interactions can lead to momentum exchange between the ballistic jet
and the surrounding electron fluid, resulting in a depletion of electrons in vicinity of the main
jet and extraction of electrons from the nearby detector aperture. The experimental results are
compared to the predictions of theoretical models based on Boltzmann transport equations.