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

TL;DR

This study investigates how substrate spin-orbit coupling influences the topological gap in magnetic impurity chains, revealing that stronger SOC enhances the minigap, which is crucial for realizing Majorana states.

Contribution

The paper provides the first experimental comparison of the effects of increased substrate spin-orbit coupling on Shiba chains using scanning tunneling spectroscopy.

Findings

Stronger SOC increases the minigap by a factor of 1.9.

The dispersion of the dominant Shiba band is similar across different substrates.

Enhanced SOC correlates with larger topological gaps in 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 $\varDelta$, is increased by a factor of 1.9 with respect to the Nb case, which can be ascribed to the stronger SOC.