Atomic line defects and zero-energy end states in monolayer Fe(Te,Se) high-temperature superconductors

Majorana zero-energy bound states have been proposed to exist at the ends of one-dimensional Rashba nanowires proximity-coupled to an s-wave superconductor in an external magnetic field(1,2). Such hybrid structures are a central platform in the search for non-Abelian Majorana zero modes that may be applied in fault-tolerant topological quantum computing(3,4). Here we report the discovery of zero-energy bound states simultaneously appearing at both ends of a one-dimensional atomic line defect in monolayer iron-based high-temperature superconductor FeTe0.5Se0.5 films. The spectroscopic properties of the zero-energy bound states, including the temperature and tunnelling barrier dependences, as well as their fusion induced by coupling on line defects of different lengths are found to be robust and consistent with those of the Majorana zero modes. These observations suggest a realization of topological Shockley defects at the ends of an atomic line defect in a two-dimensional s-wave superconductor that can host a Kramers pair of Majorana zero modes protected by time-reversal symmetry along the chain. Our findings reveal a class of topological line defect excitations in two-dimensional superconductor FeTe0.5Se0.5 monolayer films and offer an advantageous platform for generating topological zero-energy excitations at higher operating temperatures, in a single material, and under zero external magnetic field. Bound states at zero energy are observed at the ends of a line defect formed of atomic vacancies on the surface of a high-temperature superconductor. This indicates the possible presence of Majorana modes.