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Updated: May 11, 2026

Scanning SQUID Study of Vortex Manipulation by Local Contact
Published on: February 1, 2017
Observation of thermally activated vortex pairs in a quasi-2D Bose gas
Jae-yoon Choi1, Sang Won Seo, Yong-il Shin
1Center for Subwavelength Optics and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
Abstract:
We measure the in-plane distribution of thermally activated vortices in a trapped quasi-2D Bose gas, where we enhance the visibility of density-depleted vortex cores by radially compressing the sample before releasing the trap. The pairing of vortices is revealed by the two-vortex spatial correlation function obtained from the vortex distribution. The vortex density decreases gradually as temperature is lowered, and below a certain temperature, a vortex-free region emerges in the center of the sample. This shows the crossover from a Berezinskii-Kosterlitz-Thouless phase containing vortex-pair excitations to a vortex-free Bose-Einstein condensate in a finite-size 2D system.
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