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Thursday, June 11, 2009
12:30 PM - 1:30 PM
T-DO Conference Room (Bldg 123, Room 121)

Quantum Lunch

Vortex dipole formation and dynamics in highly oblate Bose-Einstein condensates

Ashton Bradley
University of Otago, Dunedin, New Zealand

Vortices in superfluids are the quanta of angular momentum. They have been created in trapped Bose-Einstein condensates (BEC) using a range of techniques for imparting angular momentum to the trapped atoms, including manipulating the trapping potentials, spinning up a thermal gas and then evaporating, using two-photon Raman transitions, merging multiple BECs, or by exploiting spontaneous processes occurring during the BEC phase transition.

In this work we experimentally create vortex-antivortex pairs by swiping an optical potential through a trapped oblate BEC - a process which imparts negligible angular momentum to the condensate. Through careful control of the stirring potential we find that long lived single and multiple vortex-dipoles can be created. High shot-to-shot repeatability allows the resolution of vortex dynamics in absorption image sequences revealing the coherent nature of the formation process. We characterize the processes of vortex formation and decay, comparing with numerical simulations using c-field methods for modeling finite temperature Bose gases.

Host: David Roberts, T-CNLS/T-4