Spectroscopic Evidence of Edge-Localized States in an Antiferromagnet Topological Insulator NdBi

Materials exhibiting non-trivial topology and magnetism hold the promise of hosting 1D chiral edge states, which can carry dissipationless currents and, when proximitized to a superconductor, develop Majorana modes. However, persistent materials challenges arising from magnetic and electronic disorder have hindered the realization and measurement of these states, and limited the observation of the Quantum Anomalous Hall effect to low temperatures. Here we study the topological antiferromagnet NdBi, which belongs to a new class of magnetic topological materials, i.e., rare earth monopnictides. These binary topological compounds with intrinsic magnetism are not plagued by the same materials issues and may potentially offer a new platform for hosting 1D edge states. By combining spin-polarized scanning tunneling microscopy (STM) with quasiparticle interference, we successfully identify distinct signatures of the ferromagnetic (FM) and antiferromagnetic (AFM) terminations. Crucially, we demonstrate that step edges on ferromagnetic surfaces, which serve as magnetic domain walls, host well-defined 1D edge modes that vanish above the Néel temperature. Our findings position NdBi as a promising platform for further explorations of 1D chiral edge modes and future realizations of Majorana states in proximitized rare-earth mono-pnictides.