Transient Response of Superconducting Microbridges to Supercritical Currents.

We have made time-resolved measurements of the voltage waveforms on one-dimensional superconducting strips caused by current pulses in excess of their critical currents. We report the first known observations of the kinetic inductance spike the non-zero minimum voltage, and the time-domain development of phase-slip centers. These measurements were made on indium microbridges and represent an important extension of the work of Pals and Wolter to a higher critical temperature material. We have also measured the delay time between the application of the current pulse and the development of the first phase slip center in these bridges and have used it in conjunction with the SST theory (Schmidt, Schon and Tinkham 1980) to estimate a Tau sub E of 140 picoseconds for indium. In addition we have made a few measurements on dirty aluminum strips which also show the time domain development of phase slip centers. We have compare the data with the nonequilibrium superconductivity theory SST wherever possible. To do this, we have developed a computer program that approximation. From these numerical solutions we have found that, for the most part, the theory is in good agreement with the data. We have also used this exact solution to test the validity of several simpler approximations.
Sponsored in part by Grant NSF-DMR79-04155.