Vortex formation in a stirred Bose-Einstein condensate

Vortex formation in a stirred Bose-Einstein condensate

December 22, 1999 | K. W. Madison, F. Chevy, W. Wohlleben, J. Dalibard
A Bose-Einstein condensate (BEC) of rubidium atoms is stirred using a focused laser beam, leading to the formation of vortices when the stirring frequency exceeds a critical value. The study observes up to four vortices simultaneously and measures the lifetime of a single vortex state after the stirring is stopped. Vortices in superfluids, first observed in liquid helium, exhibit quantized circulation and are absent at low rotation frequencies but appear as singularities in the velocity field at higher frequencies. In this experiment, vortices are generated in a gaseous BEC by creating an anisotropic potential with a stirring laser beam, mimicking the "rotating bucket" experiment. The critical rotation frequency for vortex formation is determined, and the metastability of the vortex state is analyzed. The vortex core size is found to be on the order of the healing length, and the vortex lifetime is measured to be several hundred milliseconds with non-exponential decay. The study also reveals that multiple vortices can form at higher rotation frequencies, often in symmetric configurations. The results provide insights into the stability and dynamics of vortices in BECs, and the experiment highlights the importance of thermal and rotational effects in superfluid systems. The findings contribute to understanding the behavior of vortices in quantum gases and their potential applications in superfluidity research.A Bose-Einstein condensate (BEC) of rubidium atoms is stirred using a focused laser beam, leading to the formation of vortices when the stirring frequency exceeds a critical value. The study observes up to four vortices simultaneously and measures the lifetime of a single vortex state after the stirring is stopped. Vortices in superfluids, first observed in liquid helium, exhibit quantized circulation and are absent at low rotation frequencies but appear as singularities in the velocity field at higher frequencies. In this experiment, vortices are generated in a gaseous BEC by creating an anisotropic potential with a stirring laser beam, mimicking the "rotating bucket" experiment. The critical rotation frequency for vortex formation is determined, and the metastability of the vortex state is analyzed. The vortex core size is found to be on the order of the healing length, and the vortex lifetime is measured to be several hundred milliseconds with non-exponential decay. The study also reveals that multiple vortices can form at higher rotation frequencies, often in symmetric configurations. The results provide insights into the stability and dynamics of vortices in BECs, and the experiment highlights the importance of thermal and rotational effects in superfluid systems. The findings contribute to understanding the behavior of vortices in quantum gases and their potential applications in superfluidity research.
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