Observation of Edge States in Multilayer WTe₂

Three-dimensional (3D) topological semimetals possess unconventional surface and edge states, which play central roles in exotic topological phases. WTe₂, as a type-II Weyl semimetal, has 2D Fermi arcs on the (001) surface in the bulk and 1D helical edge states in its monolayer. However, in the intermediate regime between the bulk and monolayer, the edge states have not been resolved owing to its closed band gap which makes the bulk states dominant. Here, we report the signatures of the edge states by superconducting quantum interference measurements in multilayer WTe₂ Josephson junctions and we directly map the localized supercurrent. In thick WTe₂ (~60 nm), the supercurrent is uniformly distributed on the (001) surface. In thin WTe₂ (10 nm), however, the supercurrent becomes confined to the 1D edge modes and its width reaches up to 1.4 um. Furthermore, an asymmetric Josephson effect , predicted as a unique characteristic of inversion-symmetry-breaking topological systems, is observed in thin WTe₂ whereas it is absent in the thick one. The ability to combine superconductivity with these edge states establishes WTe₂ as a promising topological system with exotic quantum phases and a rich physics of extra dimensionality and tunability.