Observation of a re-emergence of the flux lattice in BSCCO

We have performed detailed SANS investigations of the flux lattice in BSCCO. At fields above 600G, the diffracted intensity increases as a function of temperature above 30K. This increase in intensity indicates that the flux lattice becomes more perfect at higher temperatures. We attribute this to a weakening of pinning at higher temperatures, which allows the flux lines to relax into a more ordered configuration. This decrease in pinning strength is due to thermal fluctuations smearing out the pinning wells seen by the flux pancakes. If our interpretation is correct, our work represents the first experimental evidence for this phenomenon.