We suggest a method to experimentally obtain two-dimensional matter-wave discrete solitons with a self-repulsive Bose-Einstein condensate in optical lattices. At the edge of the Brillouin zone, a wavepacket effective mass is negative, which could be treated as an inversion of the nonlinearity sign. Above critical nonlinearity this makes the wavepackets collapse partially into localized modes with a chemical potential located in the gap between the first and the second bands. This critical nonlinearity is also associated with the smallest nonlinearity for which the discrete solitons are possible in the gap. Extensive numerical simulations for square and asymmetric honeycomb lattices in the continuous model illustrate every stage of the process.
Journal of Optics B: Quantum and Semiclassical Optics
- Pub Date:
- May 2004
- discrete solitonsBose─Einstein condensatetwo-dimensional optical lattices;
- Soft Condensed Matter
- 16 subfigures, v2: added a section on delocalization and references