Observation of topological states residing at step edges of WTe ₂

Abstract

Topological states emerge at the boundary of solids as a consequence of the nontrivial topology of the bulk. Recently, theory predicts a topological edge state on single layer transition metal dichalcogenides with 1 T’ structure. However, its existence still lacks experimental proof. Here, we report the direct observations of the topological states at the step edge of WTe ₂ by spectroscopic-imaging scanning tunneling microscopy. A one-dimensional electronic state residing at the step edge of WTe ₂ is observed, which exhibits remarkable robustness against edge imperfections. First principles calculations rigorously verify the edge state has a topological origin, and its topological nature is unaffected by the presence of the substrate. Our study supports the existence of topological edge states in 1 T’-WTe ₂, which may envision in-depth study of its topological physics and device applications.

Abstract

Two-dimensional topological insulators support edge conduction electrons but its realization in real materials is rare. Here, Peng et al. report the direct observation of topological states at the step edge of WTe ₂.