Three Dimensional Skyrmions in Bose-Einstein Condensates with Discrete Internal Symmetries*

Bose-Einstein condensates (BECs) can host a wide variety of topological excitations, including vortices, domain walls, monopoles, knots, and skyrmions. The type and nature of the excitations are determined by the magnetic phase of the condensate. Skyrmions in particular are nonsingular, particle-like spin textures that appear in a variety of condensed-matter contexts. They are described mathematically by nontrivial mappings from the spatial coordinates onto the order parameter space, and characterized by a mapping degree reflecting the number of times the order parameter space is covered. We provide experimental evidence of the creation of three-dimensional skyrmions with mapping degrees as high as 8 in the magnetic phased of spin-2 BECs where the order parameter space exhibits discrete internal symmetries.