Coulomb screening of impurity charge and anomalous tunneling transparency

Abstract

This paper analyzes the effect of the screened Coulomb interaction between metallic electrons in the sidewalls, on the one hand, and a localized electron in an impurity level, on the other, on the tunneling in doped quantum structures with an intrinsic two-dimensional continuum. We show that Mahan’s non-Fermi-liquid singularity at the Fermi level is unstable against additional scattering due to tunneling. As a result, the current-voltage characteristic changes radically when the Fermi level in the sidewalls is approached by the edge of the two-dimensional band. Specifically, the peak due to the non-Fermi-liquid singularity with a section of negative differential resistance is replaced with a step-like or a two-step feature, which corresponds to a single or split Fermi-liquid resonance near the edge of the 2D band involved in the tunneling process.