Quantum oscillations in coupled single electron tunnel junctions

Abstract

It has been proposed that the frequency of the voltage oscillations associated with single electron tunneling (SET) in ultra-small junctions can be used for measuring electrical current at a higher degree of accuracy and resolution than earlier methods. To get rid of parasitic capacitances these SET junctions are made in pairs, coupled in series. A coupled nonlinear system is often expected to have complex behavior. Such complex behavior will obviously inhibit the function as a current mater. Therefore a detailed analysis of the coupled system is necessary and has been done here. We use an equivalent model to study the time dependence of the voltage oscillations across such a pair. Measurements on a test circuit as well as numerical studies of the corresponding theoretical model show that there is a large current interval where there is a simple functional relationship between the current driven through the circuit and the oscillation frequency. Multiperiodic behavior is also observed in the lower part of the current interval where oscillations are possible.