Disorder-induced vortex lattice melting in a Bose-Einstein condensate

We study the vortex lattice dynamics in the presence of a single impurity as well as random impurities or disorder. We show that in the presence of a single impurity, the vortex lattice gets distorted and the distortion depends on the position of the single impurity with respect to the positions of the vortices in the impurity-free Abrikosov vortex lattice and also on the strength of the impurity potential. We then show that a type of giant hole with hidden vortices inside it can be created in the vortex lattice by a cluster of impurities. In the presence of random impurity potential or disorder, the vortex lattice melts. We show that the vortex lattice also melts in the presence of the pseudorandom potential generated by the superposition of two optical lattices. The absence of long-range order in the melted vortex lattice is demonstrated from the structure factor profile and the histogram of the distances between each pair of vortices.