  We describe both experimentally and theoretically a hydrodynamic pumping
mechanism in a Fermi liquid, arising from electron-electron interaction. An
electron beam sweeping past an aperture is observed to pump carriers from this
aperture. Experimentally, the pumping effect induces a current in the lead
connected to the aperture, or induces a voltage signal corresponding to carrier
extraction from the lead. Different geometries display the effect, and this
work discusses one experimental geometry in detail. Theoretically, the solution
of the Boltzmann equation, including an electron-electron collision integral,
shows that the potential induced by injected electrons becomes positive in the
regions nearby the main stream of injected electrons. Thus, the repulsive
Coulomb interaction leads to an attractive, pumping force in the Fermi liquid.
The pumping mechanism here described is shown to be qualitatively different
from the Bernoulli pumping effect in classical liquids.
