Role of Arsenic in Iron-based Superconductivity at Atomic Scale

TL;DR

This study uses atomic-scale STM/S techniques to reveal how arsenic atoms influence superconductivity in iron-based materials by directly observing Fe-As interactions and their impact on electronic properties.

Contribution

The paper provides direct atomic-scale evidence of arsenic's crucial role in iron-based superconductivity through STM/S experiments.

Findings

Arsenic removal suppresses superconductivity at the atomic scale.

Adding arsenic restores local superconducting features.

Fe-As hybridization is key to superconductivity in these materials.

Abstract

In iron-based superconductors, a unique tri-layer Fe-As (Se, Te, P) plays an essential role in controlling the electronic properties, especially the Cooper pairing interaction. Here we use scanning tunneling microscopy/spectroscopy (STM/S) to investigate the role of arsenic atom in superconducting Ba0.4K0.6Fe2As2 by directly breaking and restoring the Fe-As structure at atomic scale. After the up-As-layer peeled away, the tunneling spectrum of the exposed iron surface reveals a shallow incoherent gap, indicating a severe suppression of superconductivity without arsenic covering. When a pair of arsenic atoms is placed on such iron surface, a localized topographic feature is formed due to Fe-As orbital hybridization, and the superconducting coherent peaks recover locally with the gap magnitude the same as that on the iron-layer fully covered by arsenic. These observations unravel the Fe-As interactions on an atomic scale and imply its essential roles in the iron-based superconductivity.