AQP -seminaari: Eccentric fractional skyrmions in a magnetic quantum fluid
Skyrmion is a sort of topological soliton that occurs after the phase transition accompanying spontaneous symmetry breaking. Magnetic skyrmions, known in magnets, “carry” a characteristic pattern (texture) in the order parameter (vector) field, like an electron in two dimensions. The “charge” of a skyrmion is topologically quantized and the state with an elementary charge is typically sketched as in the left panel of Figure. The current work reveals that a skyrmion can have a half of the elementary charge in a magnetic quantum fluid of 7Li Bose-Einstein condensates, called the eccentric fractional skyrmion (EFS) . An EFS is distinguished form a meron that can only exist as a pair of them. An EFS is isolated and has an eccentric “shaft” as a spin singularity (the right panel). It is shown that EFSs are generated from the spin-current instability that can be regarded as the magnetic quantum fluid equivalent of the Kelvin-Helmholtz instability known in fluid dynamics.
 Hiromitsu Takeuchi, Phys. Rev. A 105, 013328 (2022)