RESONANT-TUNNELING AND LOW-ENERGY IMPURITY BEHAVIOR IN A RESONANT-LEVEL MODEL

We study the effect of screening of an impurity charge by conduction electrons on resonant tunneling at arbitrary energy of the impurity level. We examine the exactly solvable model of the resonant level. We find the ground-state solutions of the model at all possible Coulomb interactions. The principle of equivalence between its universal behavior and the Kondo model is proved. However, the dependence of its scale invariant variable on the bare variables has different forms in two different regions of the parameter variations. This means that besides the well-known Kondo-like fixed point of the renormalization at weak Coulomb interaction a new stable point exists. The latter determines a singular low-energy behavior of the impurity. Based on the solution, the tunneling amplitude is calculated. It is shown that for a narrow gap or quasi-one-dimensional junction a severe renormalization of the one-electron half-width GAMMA0 occurs GAMMA(R) is-proportional-to GAMMA0(GAMMA0/D)alpha/(1-alpha). The comparison with perturbation results is discussed. Finally the conductance of the junction with randomly located impurities is calculated to clarify the crucial role of the non-Fermi-liquid behavior on the resonant tunneling under certain conditions.