Towards a circuit theory for metallic single‐electron tunnelling devices

A circuit theory for metallic single‐electron tunnelling (SET) junctions is presented. In detail circuits with a single SET junction in arbitrary environments are described. Based on the conservation of energy in the circuits—a fundamental circuit theorem—equivalent circuit elements are proposed and possible physical justifications are presented. The resulting model represents the tunnel event by an impulse current source, the junction by a charged capacitor, and the tunnelling condition as a discrete process based on local circuit parameters—and may include a tunnelling time. Simple examples illustrate Coulomb blockade, Coulomb oscillations, and continuous direct tunnelling.