Equilibrium tunneling from the two-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 $k_B$T. 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×${10}^{11}$ to 6×${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}2}$. 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.