Observation of topological superconductivity on the surface of an iron-based superconductor

TL;DR

This paper reports the discovery of topological superconductivity on the surface of an iron-based superconductor, FeTe0.55Se0.45, which hosts Dirac-cone surface states with an s-wave superconducting gap, offering a promising platform for Majorana fermions.

Contribution

It demonstrates that FeTe0.55Se0.45 exhibits 2D topological superconductivity on its surface, providing a simpler and potentially higher-temperature platform for Majorana fermions compared to previous methods.

Findings

Identified Dirac-cone spin-helical surface states at the Fermi level.

Observed an s-wave superconducting gap below Tc.

Proved the surface states are 2D topologically superconducting.

Abstract

Topological superconductors, whose edge hosts Majorana bound states or Majorana fermions that obey non-Abelian statistics, can be used for low-decoherence quantum computations. Most of the proposed topological superconductors are realized with spin-helical states through proximity effect to BCS superconductors. However, such approaches are difficult for further studies and applications because of the low transition temperatures and complicated hetero-structures. Here by using high-resolution spin-resolved and angle-resolved photoelectron spectroscopy, we discover that the iron-based superconductor FeTe1-xSex (x = 0.45, Tc = 14.5 K) hosts Dirac-cone type spin-helical surface states at Fermi level, which open an s-wave SC gap below Tc. Our study proves that the surface states of FeTe0.55Se0.45 are 2D topologically superconducting, and thus provides a simple and possibly high-Tc platform for realizing Majorana fermions.