Solitons in quasi-one-dimensional Bose-Einstein condensates with competing dipolarand local interactions

摘要

We study families of one-dimensional matter-wave bright solitons supported by the competition of contactand dipole-dipole (DD) interactions of opposite signs. Soliton families are found, and their stability is inves-tigated in the free space and in the presence of an optical lattice (OL). Free-space solitons may exist with anarbitrarily weak local attraction if the strength of the DD repulsion is fixed. In the case of the DD attraction,solitons do not exist beyond a maximum value of the local-repulsion strength. In the system which includes theOL, a stability region for subfundamental solitons is found in the second finite band gap. For the existence ofgap solitons (GSs) under the attractive DD interaction, the contact repulsion must be strong enough. In theopposite case of the DD repulsion, GSs exist if the contact attraction is not too strong. Collisions betweensolitons in the free space are studied too. In the case of the local attraction, they merge or pass through eachother at small and large velocities, respectively. In the presence of the local repulsion, slowly moving solitonsbounce from each other