Zero-Energy Vortex Bound State in Iron-Based Superconductor Fe (Se, Te)

Abstract

At the surface of Fe (Se, Te), where topological superconductivity emerges, vortex cores are expected to host Majorana Fermions. Using a dilution-refrigerator STM, we have systematically examined a large number of vortices in Fe (Se, Te). We found that some vortices possess the Zero-energy Vortex Bound State (ZVBS) below 20 μeV, which suggests its Majorana bound state origin. However, we also found vortices without the ZVBS. Interestingly, emergence of the ZVBS is not related to the preexisting quenched disorders, and the fraction of vortices with the ZVBS decreases with increasing magnetic field, suggesting the importance of the inter-vortex interaction for the ZVBS formation. These results provide the necessary conditions to realize the ZVBS, leading a way to control of Majorana quasiparticles for future applications.