Are end states of magnetic atom chains on superconductors Majorana modes
In plain words
Chains of iron atoms on superconducting lead show zero-energy states at their ends that were proposed as Majorana modes, but ordinary bound states can look similar, and the identification is unsettled.
Precise statement
STM on Fe atomic chains on Pb(110) (Nadj-Perge et al., Science 346, 602, 2014, doi:10.1126/science.1259327) and on later chains assembled atom by atom on superconductors shows zero-bias features at chain ends. Determine whether these are Majorana zero modes of a topological band of hybridized Yu-Shiba-Rusinov states (bound states induced by magnetic atoms in a superconductor). Required: a resolved bulk topological gap larger than the end-mode splitting, splitting that decays exponentially with chain length, and zero-bias conductance $2e^{2}/h$ in the strong-coupling tunnelling limit. An answer is yes or no for a specified chain system.
What would settle it
Length-dependent spectroscopy on atom-by-atom assembled chains showing exponential decay of end-mode splitting with a resolved topological gap.
Status in the literature
Unverified note
Trivial interpretations of the end states are not excluded as of 2026, to this survey's knowledge.