A New Superconducting State

In long one‐dimensional superconductors, such as whiskers and thin wires, new current‐carrying states above the critical current were found that are due to spatially periodic solutions of the modulus of the order parameter and spatially periodic super and normal transport currents in parallel. The order parameter is zero a t certain points in the whisker, thereby permitting the phase of the order parameter to slip in time of one singly‐connected superconducting region with respect to the adjacent, the consequence of which is a dc potential difference between the separate singly‐connected superconducting regions. In this model the modulus of the order parameter is time‐independent, the phase is time‐dependent and the difference of the pair electrochemical potentials between adjacent singly‐connected superconducting regions is an integer fraction of the total voltage difference across the whisker. These solutions lead to voltage steps in the dc voltage‐current characteristic of thin whiskers. The upper critical current is derived at which the superconductor becomes completely normal conducting. This current is much larger than the current at which the first voltage step occurs. Agreement with experiments is good.