Experimental formation of a fractional vortex in a superconducting bi-layer

Highlights: • A fractional vortex was experimentally formed in a conventional superconductor. • The fractional vortex was realized in a superconducting bi-layer. • Multi-component quantum condensates were generated using an s-wave superconductor. - Abstract: We report the experimental formation of a fractional vortex generated by using a thin superconducting bi-layer in the form of a niobium bi-layer, observed as a magnetic flux distribution image taken by a scanning superconducting quantum interference device (SQUID) microscope. Thus, we demonstrated that multi-component superconductivity can be realized by an s-wave conventional superconductor, because, in these superconductors, the magnetic flux is no longer quantized as it is destroyed by the existence of an inter-component phase soliton (i-soliton).