Influence of electromagnetic fluctuations on electron cotunneling

We analyze electron cotunneling in systems of small normal tunnel junctions embedded in a dissipative electromagnetic environment. As an example we consider two junctions in series with an Ohmic resistor R. We show that at low voltages the electromagnetic fluctuations can suppress the cotunneling current strongly I∝${\mathit{V}}^{3+2\mathit{z}}$, where z=${\mathit{Re}}^2$/h. This effect can be used to improve the accuracy of prototypes of the single-electron dc current standard (the pump and the turnstile device).