Surface reconstruction and charge modulation in BaFe2As2 superconducting film

TL;DR

This study investigates the surface structure and electronic properties of epitaxially grown Ba(Fe1-xCox)2As2 superconducting films, revealing differences from bulk crystals but similar superconducting transport properties.

Contribution

It provides detailed surface and electronic characterization of epitaxial BaFe2As2 films, highlighting differences from bulk and the presence of charge density waves.

Findings

Different surface reconstruction compared to bulk crystals

Superconducting transport properties are similar to bulk

Charge density wave observed at the surface

Abstract

Whether or not epitaxially grown superconducting films have the same bulk-like superconducting properties is an important concern. We report the structure and the electronic properties of epitaxially grown Ba(Fe1-xCox)2As2 films using scanning tunneling microscopy and scanning tunneling spectroscopy (STS). This film showed a different surface structure, (2sqrtx2sqrt2)R45 reconstruction, from those of as-cleaved surfaces from bulk crystals. The electronic structure of the grown film is different from that in bulk, and it is notable that the film exhibits the same superconducting transport properties. We found that the superconducting gap at the surface is screened at the Ba layer surface in STS measurements, and the charge density wave was observed at the surface in sample in the superconducting state.