Theory of the voltage biased Josephson model

Abstract

The voltage biased weak link between two bulk superconductors is discussed using the conventional Josephson pendulum model. A parameter lambda is introduced to characterize the ratio between the electron pair tunnelling energy and the electrostatic energy required to store one electron pair in the link. If lambda is small, the Q-V curve, the relationship between the applied voltage and the charge stored in the link, is in a staircase form. When there are strong pair tunnelling processes, lambda >>1, the Q-V curve becomes a straight line. These results are consistent with experimental findings.