Discovery of a 1D edge mode in a Magnetic Topological semimetal

TL;DR

This paper reports the discovery of robust 1D chiral edge modes at ferromagnetic domain walls in NdBi, a magnetic topological semimetal, using spin-polarized STM, revealing potential for Majorana state realization.

Contribution

It demonstrates the existence of well-defined 1D edge modes at ferromagnetic domain walls in NdBi, linking magnetic domain structure with topological edge states.

Findings

Identification of 1D edge modes at ferromagnetic domain walls

Edge modes vanish above the Nél temperature

Correlation between magnetic surface termination and topological states

Abstract

In rare-earth monopnictides like NdBi, the interplay between magnetism and topology results in an extremely unusual topological semimetal phase which simultaneously hosts Weyl points with Fermi arcs as well as massive and massless Dirac cones. A central question in this class of materials is whether ferromagnetic surfaces with gapped Dirac cones can also host robust well-defined chiral edge states. In this study, we use spin-polarized scanning tunneling microscopy (SP-STM) and spectroscopy to investigate the correlation between the magnetic and topological properties of NdBi. By combining SP-STM imaging with quasiparticle interference, we identify distinct signatures of both antiferromagnetic and ferromagnetic surface terminations and correlate them with their respective band structures. Crucially, we demonstrate that step edges on the ferromagnetic surface which serve as magnetic domain walls host well-defined one-dimensional (1D) edge modes that vanish above the N\'eel 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 monopnictides.