Generating periodic interference in Bose-Einstein condensates

The interference between two condensates with repulsive interaction is investigated numerically by solving the one-dimensional time-dependent Gross-Pitaevskii equation. The periodic interference pattern forms in two condensates, which are prepared in a double-well potential consisting of two truncated harmonic wells centered at different positions. Dark solitons are observed when two condensates overlap. Due to the existence of atom-atom interactions, atoms are transferred among the ground state and the excited states, which coincides with the condensate energy change.