Reentrant resonant tunneling

We study the effect of electron-electron interactions on the resonant-tunneling spectroscopy of the localized states in a barrier. Using a simple model of three localized states, we show that, due to the Coulomb interactions, a single state can give rise to two resonant peaks in the conductance as a function of gate voltage, G(V_g). We also demonstrate that an additional higher-order resonance in between these two peaks becomes possible due to the resonant-tunneling process involving two-electron transitions. We have observed both these effects in GaAs transistor microstructures by studying the time evolution of three adjacent G(V_g) peaks caused by fluctuating occupancy of an isolated impurity (modulator). © 1996 The American Physical Society.