Discretized topological Hall effect emerging from skyrmions in constricted geometry

We investigate the skyrmion formation process in nanostructured FeGe Hall-bar devices by measurements of the topological Hall effect, which extracts the winding number of a spin texture as an emergent magnetic field. Stepwise profiles of the topological Hall resistivity are observed in the course of varying the applied magnetic field, which arise from instantaneous changes in the magnetic nanostructure such as the creation, annihilation, and jittering motion of skyrmions. The discrete changes in the topological Hall resistivity demonstrate the quantized nature of an emergent magnetic flux inherent in each skyrmion, which had been indistinguishable in many-skyrmion systems on a macroscopic scale.