Evidence for Majorana bound state in an iron-based superconductor

TL;DR

This paper reports the observation of a Majorana bound state in an iron-based superconductor using scanning tunneling microscopy, providing a promising platform for topological quantum computation at higher temperatures.

Contribution

It demonstrates the detection of a nearly pure Majorana bound state in FeTe1-xSex, advancing the understanding of topological superconductivity in iron-based materials.

Findings

Sharp zero-bias peak observed in vortex core

Peak remains non-split under various conditions

Supports existence of a nearly pure Majorana bound state

Abstract

The search for Majorana bound state (MBS) has recently emerged as one of the most active research areas in condensed matter physics, fueled by the prospect of using its non-Abelian statistics for robust quantum computation. A highly sought-after platform for MBS is two-dimensional topological superconductors, where MBS is predicted to exist as a zero-energy mode in the core of a vortex. A clear observation of MBS, however, is often hindered by the presence of additional low-lying bound states inside the vortex core. By using scanning tunneling microscope on the newly discovered superconducting Dirac surface state of iron-based superconductor FeTe1-xSex (x = 0.45, superconducting transition temperature Tc = 14.5 K), we clearly observe a sharp and non-split zero-bias peak inside a vortex core. Systematic studies of its evolution under different magnetic fields, temperatures, and tunneling barriers strongly suggest that this is the case of tunneling to a nearly pure MBS, separated from non-topological bound states which is moved away from the zero energy due to the high ratio between the superconducting gap and the Fermi energy in this material. This observation offers a new, robust platform for realizing and manipulating MBSs at a relatively high temperature.