Computational Study of Vortex Dynamics in Bose-Einstein Condensates in a Harmonic + Bubble Trap*

Tomoki Imura, Elisha Haber, Rachel Stromswold, Jessica Jenick, Nicholas Bigelow, University of Rochester, Rochester, NY 14627.

 

The study of vortices in Bose—Einstein condensates (BECs) is a valuable platform in quantum simulation for studying long-range interactions, lattices, quantum turbulence, and even cosmic strings. For BECs in harmonic traps, interactions between the condensed and thermal atoms will lead to dissipation, and cause vortices to eventually spiral out of the BEC. This process typically takes place on the order of seconds. In our proposal, we consider an ⁸⁷Rb BEC where two pairs of crossed Gaussian beams create a low-density spherical region at the center of a harmonically confined BEC with a high-density spherical shell surrounding it. This interior bubble profile is realized by choosing the beam wavelengths such that the usual second-order contribution of the fields is canceled out, which allows the third-order (spherical) term to dominate. Due to dissipation, vortices in BECs follow the local density gradient and migrate toward regions of lower condensate density, which in our setup is the center of the BEC rather than the edges as in the usual case. Thus, we expect this setup will extend the lifetime of vortices in BECs. To study the vortex dynamics, we solved the dissipative Gross—Pitaevskii equation (GPE) using the Crank-Nicolson method. We initialized the BEC in the trap, created one or more vortices at various locations by phase imprinting, and tracked their evolution. In the future, we will study the extended lifetime of vortices in this trap using the stochastic GPE.