Rotating vortex lattice in a Bose-Einstein condensate trapped in combined quadratic and quartic radial potentials - art. no. 063608

A dense vortex lattice in a rotating dilute Bose-Einstein condensate is stu died with the Thomas-Fermi approximation. The upper critical angular veloci ty Omega (c2) occurs when the intervortex separation b becomes comparable w ith the vortex-core radius xi. For a radial harmonic trap, the loss of conf inement as Omega-->omega (perpendicular to) implies a singular behavior. In contrast, an additional radial quartic potential provides a simple model f or which Omega (c2) is readily determined. Unlike the case of a type-II sup erconductor at fixed temperature, the onset of Omega (c2) arises not only f rom decreasing b but also from increasing xi caused by the vanishing of the chemical potential as Omega-->Omega (c2).