Coupling of Yu-Shiba-Rusinov states in one-dimensional chains of Fe atoms on Nb(110)

The hybridization of Yu-Shiba-Rusinov (YSR) states in dimers of magnetic impurities leads to molecularlike bonding and antibonding modes. In many-impurity systems, the interaction gives rise to YSR bands and can even result in the formation of a topologically nontrivial superconducting state, characterized by Majorana fermions at the edges of the system. To obtain a more detailed understanding of these interactions, we investigate the coupling of YSR states in short one-dimensional Fe chains on clean Nb(110). We observe a splitting of the single-atom YSR peaks into multiple states with even or odd spatial symmetry and identify a peculiar dependence of the even and odd states' energy position on the chain length.