AQP Seminar: Eccentric fractional skyrmions in a magnetic quantum fluid

Aalto Quantum Physics Seminars (Hybrid). Speaker: Dr. Hiromitsu Takeuchi (Department of Physics and Nambu Yoichiro Institute of Theoretical and Experimental Physics (NITEP), Osaka Metropolitan University (former Osaka City University) )
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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) [1]. 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. 



[1] Hiromitsu Takeuchi, Phys. Rev. A 105, 013328 (2022)


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