  We explore the acoustic phonon-based interaction between two neighboring
coplanar circuits containing semiconductor quantum point contacts in a
perpendicular magnetic field B. In a drag-type experiment, a current flowing in
one of the circuits (unbiased) is measured in response to an external current
in the other. In moderate B the sign of the induced current is determined
solely by the polarity of B. This indicates that the spatial regions where the
phonon emission/reabsorption is efficient are controlled by magnetic field. The
results are interpreted in terms of non-equilibrium transport via skipping
orbits in two-dimensional electron system.
