at the nanoscale*

Tungsten ditelluride (WTe₂) is a transition metal dichalcogenide whose physical properties depend critically on the number of layers. We use apertureless scattering-type near-field optical microscopy operating at Terahertz (THz) frequencies and cryogenic temperatures to identify distinct THz range electromagnetic behavior of WTe₂ mono-, bi- and tri-layer terraces in the same micro-crystals. We observed clear metallic behavior of the near-field signal on tri-layer regions. Our data are consistent with the existence of surface plasmon polaritons (SPP) in the THz range confined to tri-layer terraces in our specimens. The near-field signal on bi-layer regions surprisingly shows moderately metallicity, but with negligible temperature dependence. Subdiffractional THz imaging data together with theoretical calculations considering thermally activated carriers favor the semimetal scenario over the semiconductor scenario for bi-layer WTe₂. THz images for monolayer terraces uncovered weakly insulating behavior consistent with transport data.