Non-Topological Edge-Localized Yu-Shiba-Rusinov States in CrBr$_3$/NbSe$_2$ Heterostructures

TL;DR

This study investigates CrBr3/NbSe2 heterostructures using STM and spectroscopy, finding non-topological Yu-Shiba-Rusinov states at edges and no evidence of topological superconductivity, highlighting complex magnetic-superconductor interactions.

Contribution

The paper provides detailed experimental evidence showing the absence of topological superconductivity in CrBr3/NbSe2 heterostructures and characterizes edge-localized YSR states.

Findings

Superconducting gap unaffected by magnetism inside CrBr3 islands

Yu-Shiba-Rusinov states observed at island edges

No signatures of topological superconductivity detected

Abstract

Topological superconductivity is predicted to emerge in certain magnet-superconductor hybrid systems. Here, we revisit the heterostructure of insulating monolayer CrBr$_3$ and NbSe$_2$, for which different conclusions on the presence of topological superconductivity have been reported. Using low-temperature scanning tunneling microscopy and (shot noise) spectroscopy, we find that the superconducting gap well inside the CrBr3 islands is not affected by magnetism. At the island edges, we observe Yu-Shiba-Rusinov (YSR) states at a variety of in-gap positions, including zero energy. The absence of topological superconductivity is verified by extensive dI/dV measurements at the CrBr$_3$ island edges. Our results ask for a more detailed understanding of the interaction between magnetic insulators and superconductors.