Bose-Einstein condensates in a ring optical lattices trap

The evolution of Bose-Einstein condensates (BECs) loaded into a periodic ring optical lattices (OL) trap is studied. By means of the variational method and direct numerical simulations of the Gross-Pitaevskii (GP) equation, the ground state properties and the vortex stabilities of the condensates for both repulsive and attractive cases are investigated. The results show that the bound states exist for determinate OL strength and interatomic interaction. However, the ground states of BECs undergo delocalizing-localizing transition for both attractive and repulsive cases as the strength of the OL or the interatomic interaction is decreased below the critical value. The ring OL can suppress the delocalizing transition efficiently. (c) 2006 Elsevier B.V. All rights reserved.