Thermal enhancement of cotunneling in ultra-small tunnel junctions

Abstract

We have measured the cotunneling current below the Coulomb blockade threshold in a circuit of two ultra-small metallic tunnel junctions. The thermal enhancement of cotunneling, as well as the island-charge dependence, is in excellent agreement with theory. Circuit parameters were measured enabling theoretical and experimental values for the cotunneling current to be compared without adjustable parameters. This comparison yielded agreement within the 15% uncertainty of the experiment. Data showing the cotunneling current near the threshold voltage are also presented.