jpg, 28 kB

Observation of vortex lattices. The examples shown contain (A) 16 (B) 32 (C) 80 and (D) 130 vortices. The vortices have "crystallized" in a triangular pattern. The diameter of the cloud in (D) was 1 mm after ballistic expansion which represents a magnification of 20. Slight asymmetries in the density distribution were due to absorption of the optical pumping light.

jpg, 123 kB

The images show quantum vortices in a rotating condensate of sodium atoms. A condensate 60 micrometer in diameter and 250 micrometer in length was set in rotation by rotating laser beams. It then formed a regular lattice of vortices. The condensate was then allowed to ballistically expand which resulted in a twenty times magnification. The images represent two-dimensional cuts through the density distribution and show the density minima due to the vortex cores. The examples shown contain 0, 16, 70 and 130 vortices. The diameter of the cloud was about 1 mm.

jpg, 107 kB

Vortex lattices with defects. On the left side, the lattice has a dislocation near the center of the condensate. In the right image, there is a defect reminiscent of a grain boundary.