Macroscopic vortex droplets in Bi2Sr2CaCu2O8 crystals pumped by an ac magnetic field.

The formation of droplets (or breathers) of vortex matter in Bi(2)Sr(2)CaCu(2)O(8) crystals pumped by the low-frequency ac magnetic field is observed by magneto-optic imaging. The droplets nucleate at the points of crossing the planar defects. The magnetic flux in the droplet and the droplet size increase with time. When the flux in the droplet exceeds a critical value, the droplet shifts along the defect to the sample bulk and a new droplet with the opposite flux direction starts to nucleate at the same point. As a result, a beadlike structure of the droplets arises along the defect. A possible explanation of the phenomenon is proposed.