Topological surface superconductivity in FeSe0.45Te0.55

Topological superconductors are expected to play an important role in the development of quantum computing devices and iron-based superconductors represent an ideal platform to explore and engineer the underlying physics. Here, the authors investigate the origin of topological superconductivity in FeSe0.45Te0.55 arising from the interplay of the superconducting gap, magnetism, and a Rashba spin-orbit interaction, and its effects on the superconductor's properties. The engineering of Majorana zero modes in topological superconductors, a paradigm for the realization of topological quantum computing and topology-based devices, has been hampered by the absence of materials with sufficiently large superconducting gaps. Recent experiments, however, have provided enthralling evidence for the existence of topological surface superconductivity in the iron-based superconductor FeSe0.45Te0.55 possessing a full s(+/-)-wave gap of a few meV. Here, we propose a mechanism for the emergence of topological superconductivity on the surface of FeSe0.45Te0.55 by demonstrating that the interplay between the s(+/-)-wave symmetry of the superconducting gap, surface magnetism, and a Rashba spin-orbit interaction gives rise to robust topological superconducting phases. Moreover, the proposed mechanism explains a series of experimentally observed hallmarks of topological superconductivity, such as the emergence of Majorana zero modes in the center of vortex cores and at the end of line defects, as well as of chiral Majorana edge modes along domain walls. We also propose that the spatial distribution of supercurrents near a domain wall is a characteristic signature measurable via a scanning superconducting quantum interference device that can distinguish between chiral Majorana edge modes and trivial in-gap states.

Automated summary

This study investigates the origin and effects of topological superconductivity in FeSe0.45Te0.55 and proposes a mechanism for its emergence on the surface. The study also explains experimentally observed hallmarks of topological superconductivity.