Fig. 1: Edge states in monolayer 1T’-WTe₂.

a STM topograph of a monolayer 1T'-WTe₂ crystal (scale bar: 5 nm). Insert: Crystal structure of the 1T'-WTe₂ crystal structure with W atoms (blue) and Te atoms (orange). Arrows represent different edge terminations. b, c Corresponding differential conductance (dI/dV) maps of the same island as in a, measured in constant height mode. d–f Spatial profile of the measured local density of state (LDOS) at 4.5 K, across the monolayer edge along the black arrow in a, and compared to a corresponding STM height profile (d). We extract a gap of ~70 meV in the 2D bulk. The data in f has been obtained by integration of the LDOS in e between E = −20 meV to E = −40 meV and shows an overall enhancement near the edge with superimposed charge density modulations also observed in b. The solid black line shows a fit to an exponential decay from which we extract a decay length of (2.1 ± 0.2) nm. Insert: Comparison of point spectra at bulk and edge, highlighting the bulk gap (black) and LDOS enhancement at the edge (blue) corresponding to the edge state. g Evolution of the edge state LDOS from the edge into the bulk (see corresponding markers in a, d). The solid black lines are fits to TLL theory (see text). All spectra have been offset for clarity, with the zero position indicated (horizontal dashed lines).