DYNAMIC REDUCTION OF THE CRITICAL CURRENT IN A JOSEPHSON JUNCTION

We have investigated the switching behavior of a Josephson tunnel junction driven by a signal with speed comparable to its plasma period τp. The Josephson junction is assumed initially to be in a static state so that the average voltage across it is zero. Application of a steplike current pulse of rise time {reversed tilde equals}τp is shown to induce switching to the finite voltage state even for values of currents much smaller than its critical current. A reduction of the critical current occurs due to the dynamic process. The approximate expressions derived show good agreement with the results obtained from simulations. The extent of dynamical reduction is limited to {reversed tilde equals}27%. Shunting of the junction can eliminate this effect. © 1990 Plenum Publishing Corporation.