Half-integer winding of order parameter in an iron-based superconductor

In an ordinary superconducting ring the quantum phase winds by whole turns, so trapped magnetic flux comes in steps of h/2e. In a topological superconductor the phase can wind by half a turn. Phase-sensitive transport measurements on Fe(Te,⁠Se) rings show quantum oscillations with half the usual flux period, the long-sought signature of half-integer winding.

• Superconducting quantum oscillations with a period of half the flux quantum, Φ₀/2.
• The oscillations are modulated by a global current–field symmetry, consistent with strong spin–orbit coupling in the condensate.
• Points toward non-Abelian excitations and scalable topological qubits.

Fig. 4 of the manuscript