Multiple topological states in iron-based superconductors

Topological materials and unconventional iron-based superconductors are both important areas of study but, to date, relatively little overlap has been identified between these two fields. However, the combination of topological bands and superconductivity promises the manifestation of exotic superconducting states, including Majorana fermions, the central component of topological quantum computation. Here, using laser-based, spin-resolved and angle-resolved photoemission spectroscopy and density functional theory calculations, we have identified both topological insulator and Dirac semimetal states near the Fermi energy in different iron-based superconducting compounds. Carrier doping can tune these topologically non-trivial bands to the Fermi energy, potentially allowing access to several different superconducting topological states in the same material. These results reveal the generic coexistence of superconductivity and multiple topological states in iron-based superconductors, indicating that this broad class of materials is a promising platform for high-temperature topological superconductivity.