Critical current and a.c. susceptibility in two-junction quantum interferometers in the presence of oscillating magnetic fields

The a.c. magnetic susceptibility and the time dependence of the critical current of a two-junction quantum interferometer are studied by means of perturbation analysis in the limit of small values of the parameter β. In this limit, it is possible to solve, in closed analytic form, the dynamical equation for the variable describing flux motion in and out the superconducting loop, in such a way that the frequency dependence of the a.c. susceptibility of these systems can be explicitly found. The critical current, corresponding to the oscillating applied flux values, is determined in the same limit.