Observation of half-quantum vorticity in an iron-based superconductor

Half-quantum vortices carry half the usual superconducting flux quantum and are predicted in superconductors whose Cooper pairs carry spin. Using mesoscopic ring devices of single-crystal Fe(Te,⁠Se), a superconductor with helical Dirac surface states, we report direct transport signatures of half-quantum vorticity.

• Half-integer quantum oscillations arising from the splitting of quantized fluxoid states.
• Distinct signatures of trapped half-integer fluxoids.
• Oscillations modulated by a background symmetry set by the relative orientation of the DC bias current and the perpendicular magnetic field, consistent with strong spin–orbit coupling.
• A step toward non-Abelian excitations in quantum materials and scalable topological qubits.