  Van der Waals (vdW) layered transition metal dichalcogenides (TMDCs)
materials are emerging as one class of quantum materials holding novel optical
and electronic properties. In particular, the bandgap tunability attractive for
nanoelectronics technology have been observed up to 1.1 eV when applying
dielectric screening or grain boundary engineering. Here we present the
experimental observation of bandgap closing at the center of the screw
dislocation-driven WS2 spiral pyramid by means of scanning tunneling
spectroscopy, which is validated by first-principle calculations. The observed
giant bandgap modulation is attributed to the presence of dangling bonds
induced by the W-S broken and the enhanced localized stress in the core of the
dislocation. Achieving this metallic state and the consequent vertical
conducting channel presents a pathway to 3D-interconnected vdW heterostructure
devices based on emergent semiconducting TMDCs.
