EQUILIBRIUM TUNNELING FROM THE 2-DIMENSIONAL ELECTRON-GAS IN GAAS - EVIDENCE FOR A MAGNETIC-FIELD-INDUCED ENERGY-GAP

Zero-bias tunneling of electrons between a quantum well and an n+ substrate is studied with excitation voltages smaller than kBT. At low temperatures and only with magnetic field applied perpendicular to the plane of the electron gas in the well, the tunneling rate develops a novel temperature-dependent suppression. The suppression strength is roughly independent of Landau-level filling for densities 0.5×1011 to 6×1011 cm-2. The data are interpreted in terms of a magnetic-field-induced energy gap, at the Fermi level, in the single-particle spectrum of electrons in the well. © 1990 The American Physical Society.