Abstract
We observe the proliferation of vortices in the Berezinskii-Kosterlitz-Thouless regime on a two-dimensional array of Josephson-coupled Bose-Einstein condensates. As long as the Josephson (tunneling) energy exceeds the thermal energy , the array is vortex free. With decreasing , vortices appear in the system in ever greater numbers. We confirm thermal activation as the vortex-formation mechanism and obtain information on the size of bound vortex pairs as is varied.
- Received 27 March 2007
DOI:https://doi.org/10.1103/PhysRevLett.99.030401
©2007 American Physical Society