Josephson effect in low-capacitance superconductor–normal-metal–superconductor systems

R. Bauernschmitt; J. Siewert; Yu. V. Nazarov; A. A. Odintsov

doi:10.1103/PhysRevB.49.4076

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Josephson effect in low-capacitance superconductor–normal-metal–superconductor systems

R. Bauernschmitt, J. Siewert, Yu. V. Nazarov, A. A. Odintsov

DOI 10.1103/PhysRevB.49.4076 · Physical Review B

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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 Ic through such a system as a function of the gate voltage Vg taking into account parity effects in the superconductors. The dependence Ic(Vg) shows resonant singularities and has a qualitatively different character for Δ<EC and Δ>EC, Δ being the superconducting gap and EC=e2/2C 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.