Abstract
The transport properties of a small superconductor–normal-metal–superconducting tunnel junction can be controlled by a gate electrode coupled capacitively to the central island. We evaluate the critical Josephson current through such a system as a function of the gate voltage taking into account parity effects in the superconductors. The dependence () shows resonant singularities and has a qualitatively different character for Δ< and Δ>, Δ being the superconducting gap and =/2C being the charging energy. Due to the sweeping of the gate voltage, the system can be driven to states which are metastable with respect to a change of the number of electrons on the central island. Since the lifetime of the metastable states can be macroscopically large, one can observe a remarkable bistability of the Josephson current. A weak magnetic field suppresses the interference of the electrons propagating through the central electrode, and, consequently, the magnitude of the critical current.
- Received 27 July 1993
DOI:https://doi.org/10.1103/PhysRevB.49.4076
©1994 American Physical Society