# Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te)

## TL;DR

This study uses high-resolution spectroscopic imaging to investigate vortex bound states in Fe(Se,Te), revealing conditions for zero-energy Majorana quasiparticles that are crucial for topological quantum computing.

## Contribution

It provides direct spectroscopic evidence of zero-energy vortex bound states in Fe(Se,Te) and clarifies their dependence on magnetic field and disorder, advancing understanding of Majorana quasiparticles.

## Key findings

- Zero-energy vortex bound states observed at 0 ± 20 μeV.
- Fraction of vortices with ZVBS decreases with magnetic field.
- Disorder does not significantly affect ZVBS occurrence.

## Abstract

Majorana quasiparticles (MQPs) in condensed matter play an important role in strategies for topological quantum computing but still remain elusive. Vortex cores of topological superconductors may accommodate MQPs that appear as the zero-energy vortex bound state (ZVBS). An iron-based superconductor Fe(Se,Te) possesses a superconducting topological surface state that has been investigated by scanning tunneling microscopies to detect the ZVBS. However, the results are still controversial. Here, we performed spectroscopic-imaging scanning tunneling microscopy with unprecedentedly high energy resolution to clarify the nature of the vortex bound states in Fe(Se,Te). We found the ZVBS at 0 $\pm$ 20 $\mu$eV suggesting its MQP origin, and revealed that some vortices host the ZVBS while others do not. The fraction of vortices hosting the ZVBS decreases with increasing magnetic field, while chemical and electronic quenched disorders are apparently unrelated to the ZVBS. These observations elucidate the conditions to achieve the ZVBS, and may lead to controlling MQPs.