Superconducting Chaos

A new experiment at Colorado State University studies the chaotic dynamics of "flux drops"-microscopic swirling eddies of supercurrent-that flow along a narrow channel crossing a superconducting strip. An applied current perpendicular to the channel causes a flux drop to nucleate, grow, and break off at the end of the channel. The drop is then driven along the channel by the current.

This process is reminiscent of water drops dripping from a nozzle, for a long time of the chief methods for understanding chaos. The Colorado State investigators used a micron-sized magnetic sensor to directly detect the magnetic field of individual drops as they passed beneath it. The resulting time sequence of flux drops, just like that of water drops from a faucet, exhibits clear signatures of deterministic chaos, implying that the irregular-looking sequence of drops is not random, but predictable from knowledge of earlier drop times.

However, predicting the sequence more than 4 or 5 drops into the future becomes exponentially difficult-another hallmark of chaos. According to Stuart Field (field@lamar.colostate.edu, 970-491-3773) this is the first conclusive observation of chaotic behavior in moving flux structures. The direct observation of the time series allows for an unambiguous identification of chaos in this system. (Field and Stan, Physical Review Letters)