Non-Majorana modes in diluted spin chains proximitized to a superconductor

• Published in: Proceedings of the National Academy of Sciences - PNAS 2022-10, Vol.119 (42), p.e2210589119-e2210589119
• Main Authors: Küster, Felix, Brinker, Sascha, Hess, Richard, Loss, Daniel, Parkin, Stuart S P, Klinovaja, Jelena, Lounis, Samir, Sessi, Paolo
• Format: Article
• Language: English
• Subjects: Adatoms; Chains; Crystallography; Dilution; Fermi surfaces; Physical Sciences; Platforms; Substrates; Superconductivity; Superconductors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2210589119

Spin chains proximitized with superconducting condensates have emerged as one of the most promising platforms for the realization of Majorana modes. Here, we craft diluted spin chains atom by atom following a seminal theoretical proposal suggesting indirect coupling mechanisms as a viable route to trigger topological superconductivity. Starting from single adatoms hosting deep Shiba states, we use the highly anisotropic Fermi surface of the substrate to create spin chains characterized by different magnetic configurations along distinct crystallographic directions. By scrutinizing a large set of parameters we reveal the ubiquitous emergence of boundary modes. Although mimicking signatures of Majorana modes, the end modes are identified as topologically trivial Shiba states. Our work demonstrates that zero-energy modes in spin chains proximitized to superconductors are not necessarily a link to Majorana modes while simultaneously identifying other experimental platforms, driving mechanisms, and test protocols for the determination of topologically nontrivial superconducting phases.