COMBINED JOSEPHSON AND CHARGING BEHAVIOR OF THE SUPERCURRENT IN THE SUPERCONDUCTING SINGLE-ELECTRON TRANSISTOR

Measurements of two ultrasmall Josephson junctions connected in series show a supercurrent with magnitude much greater than previously repor ted for similar devices. The dependence of the supercurrent on gate ch arge shows agreement with predictions made by Averin and Likharev that are based on a conjugate relationship between the junction phase and charge variables. The transport of Cooper pairs through the two juncti ons makes the devices behave effectively as a single junction whose cr itical current is modulated by the gate charge.