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 allows one to describe charging effects in systems of normal tunnel junctions in the strong tunneling regime and to obtain simple analytical expressions for the IT curves covering a wide range of temperatures and bias voltages. We fabricated and investigated experimentally several low resistive SET transistors. Good agreement between the experiment and the theory is observed. We also applied our theory to single tunnel junctions embedded in an external electromagnetic environment with a linear effective impedance Z(s)(omega) and found a remarkably good agreement with recent experimental data for such systems. (C) 2000 Published by Elsevier Science B.V. All rights reserved.