Effect of substrate spin-orbit coupling on the topological gap size of Shiba chains

Abstract

Realizing Majorana bound states in chains of magnetic impurities on $s$-wave superconducting substrates relies on a fine tuning of the energy and hybridization of the single magnetic impurity bound states and of the spin-orbit coupling (SOC). While recent experiments investigate the influence of the former two parameters, the effect of SOC remained experimentally largely unexplored. Here, we present a scanning tunneling spectroscopy study of close-packed Mn chains along the [001]-direction on Ta(110) which has almost identical atomic and surface electronic structure compared to the previously studied Nb(110) system, but a three times larger SOC. The dominant Shiba band has a very similar dispersion, but its minigap, taken relative to $\Delta$, is increased by a factor of 1.9 with respect to the Nb case, which can be ascribed to the stronger SOC.

We have reanalyzed the experimental data in this manuscript by comparison to extensive first-principles calculations. A new interpretation of the experimental data following from this comparison is published at https://doi.org/10.48550/arXiv.2504.07509