Iron-based superconductor shows long-range quantum flow at its edges

Researchers from Boston College, the University of California Irvine and Boston University report evidence of long-range, non-disruptive quantum flow at the edges of an iron-chalcogenide superconductor. This material uniquely combines superconductivity with both band topology and spontaneous time-reversal-symmetry breaking, creating conditions expected to support topological superconducting boundary states. The work demonstrates an anomalous conductance plateau persisting over micrometer-scale separations, requiring sharp edges for sustained electron flow and exhibiting reduced thermal decoherence. This boundary-mediated transport is absent in comparable, topologically trivial materials. Iron-chalcogenide superconductors demonstrate a transport response dependent on both material topology and the sharpness of its edges. Conventional Andreev spectra are observed in topologically trivial materials regardless of edge quality, but a distinct conductance plateau emerges in topological samples only when connected to continuous, sharp edges. This finding establishes a stringent test for identifying boundary-mediated superconducting transport, differentiating it from localized responses. The research focuses on iron-chalcogenide materials, specifically Fe(Te,Se), which uniquely combine superconductivity with a topologically nontrivial electronic structure and spontaneous time-reversal symmetry breaking (TRSB). The emergence of TRSB within the superconducting state of Fe(Te,Se) provides a critical symmetry-breaking scale directly comparable with transport measurements, and experiments reveal spontaneous magnetization coinciding with superconductivity across multiple compositions. This co-existence…