Spin-orbit coupling induced splitting of Yu-Shiba-Rusinov states in antiferromagnetic dimers

TL;DR

This study investigates how spin-orbit coupling influences the hybridization and splitting of Yu-Shiba-Rusinov states in magnetic dimers on a superconductor, revealing effects relevant for topological superconductivity.

Contribution

It provides the first detailed analysis of spin-orbit coupling effects on Shiba state hybridization in magnetic dimers, including experimental observations and theoretical explanations.

Findings

Shiba states split upon dimer formation for both ferromagnetic and antiferromagnetic alignments.

Unexpected splitting in antiferromagnetic dimers is attributed to spin-orbit coupling and surface inversion symmetry breaking.

Results highlight factors affecting Shiba band formation and topological properties.

Abstract

Magnetic atoms coupled to the Cooper pairs of a superconductor induce Yu-Shiba-Rusinov states (in short Shiba states). In the presence of sufficiently strong spin-orbit coupling, the bands formed by hybridization of the Shiba states in ensembles of such atoms can support low-dimensional topological superconductivity with Majorana bound states localized on the ensembles' edges. Yet, the role of spin-orbit coupling for the hybridization of Shiba states in dimers of magnetic atoms, the building blocks for such systems, is largely unexplored. Here, we reveal the evolution of hybridized multi-orbital Shiba states from a single Mn adatom to artificially constructed ferromagnetically and antiferromagnetically coupled Mn dimers placed on a Nb(110) surface. Upon dimer formation, the atomic Shiba orbitals split for both types of magnetic alignment. Our theoretical calculations attribute the unexpected splitting in antiferromagnetic dimers to spin-orbit coupling and broken inversion symmetry at the surface. Our observations point out the relevance of previously unconsidered factors on the formation of Shiba bands and their topological classification.