Dynamic behavior and negative resistance of superconducting microbridges

In the Dayem microbridges a superconductor of very small cross section and length connects two more massive superconductors made out of the same material, tin in this case. The current-voltage characteristics and their temperature dependence near the critical temperature Tsub(c) are presented for a current source and a voltage source. Some observations made with a DC current source were recently reported. The physical interpretation was based on dynamics of vortices, and implied that there was a transition between two voltage states, leading to a plateau in current. Evidently the next step is to try to explain, within this vortex model, the features of the characteristics using a voltage source, where a strong negative resistance is observed instead of a plateau in current. (Auth.)