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

Philip Beck,András Lászlóffy,Jens Wiebe,Krisztián Palotás,László Szunyogh,Lucas Schneider,Levente Rózsa,Roland Wiesendanger

doi:10.1038/s41467-021-22261-6

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.

Highlights

Magnetic atoms coupled to the Cooper pairs of a superconductor induce Yu-Shiba-Rusinov states
The interplay between spin–orbit coupling (SOC), magnetism, and superconductivity has been extensively studied in recent years due to their applications in quantum computation, concerning the realization of topological qubits based on Majorana bound states (MBS)
Promising building blocks for the latter systems are states formed by the hybridization of Yu–Shiba–Rusinov excitations[15,16,17] which lead to the emergence of so-called Shiba bands in nanostructures

Summary

Introduction

Magnetic atoms coupled to the Cooper pairs of a superconductor induce Yu-Shiba-Rusinov states (in short Shiba states). A plethora of novel phenomena in solidstate physics has been demonstrated to arise due to the combination of SOC with inversion-symmetry breaking These include the emergence of Rashba-split surface states in the electronic structure[36]; the mechanism of the Dzyaloshinsky–Moriya interaction[37,38], which gives rise to chiral non-collinear magnetic configurations[39,40,41]; the formation of MBS in magnetic chains proximity coupled to a superconductor[42]; and the presence of the crystal anomalous Hall effect in collinear antiferromagnets[43]. We argue that considering this phenomenon is essential for understanding the subgap excitations in artificially designed magnetic nanostructures at the surfaces of superconductors

Methods

Results

Conclusion