Annihilation of quantized vorticity in a trapped Bose-Einstein condensate via the scattering of density perturbations

We evaluate the extraction of angular momentum from quantized vortices in trapped Bose-Einstein condensates. Within a variational approach we show that the energy barrier between the ground state and the state containing an axisymmetric vortex can be crossed in a scattering process by density perturbations. The transfer of angular momentum can be made total for suitably chosen density perturbations carrying about 10% of the ground-state energy, irrespectively of the number of particles in the condensate. A similar pattern is reproduced by the full solution of the Gross-Pitaevskii equation, although interference and diffusion effects are now seen to limit the efficiency of the process.