  Magnetic adatoms coupled to an $s$-wave superconductor give rise to local
bound states, so-called Yu-Shiba-Rusinov states. Focusing on the ultimate goal
of tailoring chains of such adatoms into a topologically superconducting phase,
we investigate basic building blocks - single Fe and Mn adatoms and Mn dimers
on clean superconducting Ta(110) - using scanning tunneling microscopy and
spectroscopy. We perform a systematic study of the hybridizations and
splittings in dimers, and their dependence on the crystallographic directions
and interatomic spacings, in order to identify potentially interesting chain
geometries for this novel sample type. Subsequently, we study the spin
structure as well as the length dependent Shiba band structure in Mn chains of
those geometries using spin-resolved scanning tunneling spectroscopy. All
results are compared to the according properties of structurally identical
dimers and chains on the previously studied Nb(110), which has almost identical
surface structure and electronic properties, but an about three times smaller
spin-orbit interaction.

Superconductivity