Three-dimensional vortex structure of a fast rotating Bose-Einstein condensate with harmonic-plus-quartic confinement

摘要

We address the challenging proposition of using real experimental parametersin a three-dimensional numerical simulation of fast rotating Bose-Einsteincondensates. We simulate recent experiments [V. Bretin, S. Stock, Y. Seurin andJ. Dalibard, Phys. Rev. Lett. 92, 050403 (2004); S. Stock, V. Bretin, S. Stock,F. Chevy and J. Dalibard, Europhys. Lett. 65, 594 (2004)] using an anharmonic(quadratic-plus-quartic) confining potential to reach rotation frequencies($\Omega$) above the trap frequency ($\omega_\perp$). Our numerical results areobtained by propagating the 3D Gross-Pitaevskii equation in imaginary time. For$\Omega \leq\omega_\perp$, we obtain an equilibrium vortex lattice similar (assize and number of vortices) to experimental observations. For$\Omega>\omega_\perp$ we observe the evolution of the vortex lattice into anarray of vortices with a central hole. Since this evolution was not visible inexperiments, we investigate the 3D structure of vortex configurations and3D-effects on vortex contrast. Numerical data are also compared to recenttheory [D. E. Sheehy and L. Radzihovsky, Phys. Rev. A 70, 063620 (2004)]describing vortex lattice inhomogeneities and a remarkably good agreement isfound.