Direct observation of intrinsic surface magnetic disorder in amorphous superconducting films

TL;DR

This study provides direct evidence of intrinsic surface magnetic disorder in amorphous superconducting films, highlighting its potential impact on the superconductor-insulator transition in thin films.

Contribution

It reveals that magnetic disorder exists at the surface of amorphous superconducting films without magnetic impurities, affecting superconductivity in thin films.

Findings

Magnetic disorder is present at the surface despite the absence of magnetic impurities.

Surface magnetic disorder is related to surface termination.

Bulk superconductivity persists in thicker films.

Abstract

The interplay between disorder and interactions can dramatically influence the physical properties of thin-film superconductors. In the most extreme case, strong disorder is able to suppress superconductivity as an insulating phase emerges. Due to the known pair-breaking potential of magnetic disorder on superconductors, the research focus is on the influence of non-magnetic disorder. Here we provide direct evidence that magnetic disorder is also present at the surface of amorphous superconducting films. This magnetic disorder is present even in the absence of magnetic impurity atoms and is intimately related to the surface termination itself. While bulk superconductivity survives in sufficiently thick films, we suggest that magnetic disorder may crucially affect the superconductor-to-insulator transition in the thin-film limit.