Topological Superconductivity in Fe(Te,Se) Mesoscopic Devices

A defining character of topological superconductivity is half-integer winding of the superconducting order parameter. While spectroscopic probes such as ARPES and STM have suggested topological states in Fe-based superconductors, direct transport evidence at the device scale has remained elusive. By probing nonlinear magnetoresistance in phase-sensitive transport measurements on Fe(Te,Se) mesoscopic rings, we observe oscillations with half-quantum flux periodicity, indicating half-integer winding of the order parameter. The superconducting quantum oscillations are further modulated by a global current–field symmetry, where simultaneous inversion of bias current and magnetic field leaves the oscillations invariant. The spin polarization of half-integer modes generates an effective Zeeman field resulting in a dual quantization of magnetic flux. Together, the non-trivial phase winding and signatures of a spin-textured superconducting ground state provide compelling evidence for topological superconductivity at the device scale (arXiv:2505.01522; arXiv:2508.05030).