Superconducting proximity pairing in helical edge modes, such as those of
topological insulators (TI), is predicted to provide a unique platform for
realizing Majorana zero modes (MZMs). We use scanning tunneling microscopy
measurements to probe the influence of proximity induced superconductivity and
magnetism on the helical hinge states of Bi(111) films, grown on a
superconducting Nb substrate and decorated with magnetic Fe clusters.
Consistent with model calculations, our measurements reveal the emergence of a
localized MZM at the interface between the superconducting helical edge channel
and the Fe clusters with strong magnetization component along the edge. Our
experiments also resolve the MZM spin signature that distinguishes it from
trivial in-gap states that may accidently occur at zero energy in a
superconductor
