Dynamics of multiple magnetic solitons with finite quadratic Zeeman energy

Topological defects are intriguing objects that may exist in various classical and quantum systems and may play the role of extended particles. Like atoms, multiple topological defects can also form bound states, such as breather of multiple solitons and vortex-antivortex pairs. In this talk, we report the theoretical study of the Flemish string, a bound state of a pair of magnetic solitons with opposite magnetization, which exists in the antiferromagnetic spinor BEC. Considering the SO(3)-invariant nature of the one-dimensional Gross-Pitaevskii (GP) equations with zero quadratic Zeeman shift, we analytically construct a Flemish string by rotating the dark-bright-bright (antiferromagnetic core) soliton in the Manakov limit, that is, when spin-spin interactions are neglected. The unbraiding mechanism of the Flemish string into a pair of magnetic solitons due to spin-spin interactions is addressed using perturbation theory. By applying a spatially modulated phase imprinting beam on the BEC, multiple-soliton states can be created in experiment. Our theoretical study paves the way for the further experimental investigations of soliton interactions, collisions, and of complex solitonic matter.