RESONANT-TUNNELING IN A QUANTUM NANOSYSTEM WITH AN ATTRACTIVE IMPURITY

We present the study of the conductance of a quantum nanosystem contai ning a finite-size attractive impurity. A single finite-size attractiv e impurity introduces multiple quasi-bound states in the channel for a sufficiently strong attractive potential, and these states give rise to multiple resonant peaks before the first plateau in the conductance . These resonant peaks, arising from the resonant tunneling through th e multiple quasi-bound levels, have a Lorentzian shape centered around the resonant energy and exhibit a dramatic variation in the linewidth s with resonant energy. The strength of the attractive impurity in the constriction is shown to strongly affect the resonant energy and the mean lifetime of each tunneling peak. The temperature dependence of th e resonant peaks of conductance is also discussed. (C) 1997 American I nstitute of Physics.