Coulomb blockade in a SET transistor and a single tunnel junction: Langevin equation approach

We developed a formalism, based on a quantum Langevin equation, which allow s one to describe charging effects in systems of normal tunnel junctions in the strong tunneling regime and to obtain simple analytical expressions fo r the IT curves covering a wide range of temperatures and bias voltages. We fabricated and investigated experimentally several low resistive SET trans istors. Good agreement between the experiment and the theory is observed. W e also applied our theory to single tunnel junctions embedded in an externa l electromagnetic environment with a linear effective impedance Z(s)(omega) and found a remarkably good agreement with recent experimental data for su ch systems. (C) 2000 Published by Elsevier Science B.V. All rights reserved .