Morphology Deformation and Giant Electronic Band Modulation in Long-Wavelength WS₂ Moiré Superlattices.

Abstract

As a lattice interference effect, moiré superlattices feature a magnification effect that they respond sensitively to both the extrinsic mechanical perturbations and intrinsic atomic reconstructions. Here, using scanning tunneling microscopy and spectroscopy, we observe that long-wavelength WS₂ superlattices are reconstructed into various moiré morphologies, ranging from regular hexagons to heavily deformed ones. We show that a dedicated interplay between the extrinsic nonuniform heterostrain and the intrinsic atomic reconstruction is responsible for this interesting moiré structure evolution. Importantly, the interplay between these two factors also introduces a local inhomogeneous intralayer strain within a moiré. Contrary to the commonly reported electronic modulation that occurred at the valence band edge due to interlayer hybridization, we find that this local intralayer strain induces a strong modulation at <i>K</i> point of the conduction band, reaching up to 300 meV in the heavily deformed moiré. Our microscopic explorations provide valuable information in understanding the intriguing physics in TMD moirés.