IMAGING NONEQUILIBRIUM PHONON-INDUCED BACKSCATTERING IN THE QUANTUM HALL REGIME

Nonequilibrium phonon pulses, generated by laser heating a metal film, have been used to probe small areas of an extended two-dimensional electron gas (2DEG) in a GaAs-AlGaAs heterojunction, at low temperature and in a quantizing magnetic field. The electron-phonon interaction was studied via the change in the two-terminal resistance of the 2D electron system. By scanning the phonon beam over the entire area of the 2DEG, images of the effects were made. We show that our images are in qualitative agreement with theoretical descriptions of the quantum Hall effect which include electron states confined near the edges of the 2DEG.