Effect of a perpendicular magnetic field on the zero-bias anomaly in two-dimensional electron systems

The low-energy electronic density of states (DOS) in GaAs/AlGaAs-based two-dimensional systems is investigated at mesoscopic length scales. Using nonequilibrium magnetotransport spectroscopy we find resonances in the DOS to be extremely sensitive to perpendicular magnetic fields as small as a few millitesla and to oscillate reproducibly as a function of the field. Since these resonances (also called zero-bias anomalies) are discussed as an indication of spontaneous spin polarization at low temperature, this Brief Report demonstrates a strong sensitivity of such possible polarization to magnetic fields.