Full-Gap Superconductivity in BaAs/Ferropnictide Heterostructures

TL;DR

This study reports the discovery of full-gap superconductivity at 26 K in a BaAs monolayer on ferropnictide BFCA films, with robust gaps even at monolayer thickness, highlighting the importance of heterostructure quality.

Contribution

It demonstrates full-gap superconductivity in BaAs/BFCA heterostructures, revealing the role of crystallinity and interfacial effects in enhancing superconducting properties.

Findings

Superconductivity persists at monolayer thickness.

Full-gap superconductivity observed with a maximum T_c of 26 K.

Crystallinity is crucial for the emergence of superconductivity.

Abstract

Interfacial interactions often promote the emergence of unusual phenomena in two-dimensional systems, including high-temperature superconductivity. Here, we report the observation of full-gap superconductivity with a maximal spectroscopic temperature up to 26 K in a BaAs monolayer grown on ferropnictide Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ (abbreviated as BFCA) epitaxial films. The superconducting gap remains robust even when the thickness of underlying BFCA is reduced to the monolayer limit, in contrast to the rapid suppression of $T_\textrm{c}$ in standalone BFCA thin films. We reveal that the exceptional crystallinity of the BaAs/BFCA heterostructures, featured by their remarkable electronic and geometric uniformities, is crucial for the emergent full-gap superconductivity with mean-field temperature dependence and pronounced bound states within magnetic vortices. Our findings open up new avenues to unravel the mysteries of unconventional superconductivity in ferropnictides and advance the development of FeAs-based heterostructures.