Stable singular fractional skyrmion spin texture from the quantum Kelvin–Helmholtz instability

Topology profoundly influences diverse fields of science, providing a powerful framework for classifying phases of matter and predicting nontrivial excitations. While various topological excitations have been identified within this framework, the existence of nonlinear excitations beyond it has been a subject of conjecture. In this talk, we introduce the discovery of a singular skyrmion that is stable and goes beyond the framework of topology in a ferromagnetic superfluid. The exotic skyrmions are sustained by undergoing anomalous symmetry breaking associated with the eccentric spin singularity and carry half of the elementary charge, distinct from conventional skyrmions. By successfully realizing the universal regime of the quantum Kelvin-Helmholtz instability, we identified the eccentric fractional skyrmions, produced by emission from a magnetic domain wall and a spontaneous splitting of an integer skyrmion with spin singularities.