In this experimental study, we use scanning tunneling microscopy and spectroscopy to investigate Yu-Shiba-Rusinov states induced by 4f-shell rare-earth Gd adatoms on a superconducting Nb(110) surface. We engineer Gd atom chains along the substrate's [110] and [001] directions, revealing distinct behaviors in differently oriented chains. [110]-oriented Gd chains exhibit spectroscopic features at their ends, identifying them as trivial edge states, while [001]-oriented Gd chains display zero-energy edge states, suggesting non-trivial nature. Notably, Gd chains with four atoms--independent of their particular orientation--exhibit a uniform zero-energy mode along the entire chain. These findings call for further research and a theoretical framework to describe rare-earth-based structures on superconductors.
@article{arxiv.2311.09742,
title = {Observation of zero-energy modes in Gd atomic chains on superconducting Nb(110)},
author = {Yu Wang and Felix Friedrich and Matthias Bode and Artem Odobesko},
journal= {arXiv preprint arXiv:2311.09742},
year = {2023}
}