Strain-dependent structural and electronic reconstructions in long-wavelength WS$_{2}$ moir\'e superlattices

TL;DR

This study reveals how strain-induced structural reconstructions in WS₂ moiré superlattices significantly alter their electronic properties, including large shifts in conduction band energies, through combined experimental and theoretical approaches.

Contribution

It provides a detailed microscopic understanding of how intralayer strain affects both the structural and electronic reconstructions in long-wavelength WS₂ moiré superlattices.

Findings

Atomic reconstruction forms screw dislocations and large H-stacked domains.

Moiré wavelength and geometry are tuned by intralayer heterostrain.

Conduction band K point energy shifts up to 300 meV due to strain.

Abstract

In long-wavelength moir\'e superlattices of stacked transition metal dichalcogenides (TMDs), structural reconstruction ubiquitously occurs, which has reported to impact significantly their electronic properties. However, complete microscopic understandings of the interplay between the lattice reconstruction and alteration of electronic properties, and their further response to external perturbations in the reconstructed TMDs moir\'e superlattice are still lacking. Here, using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) combined with first-principles calculation, we study the strain-dependent structural reconstruction and its correlated electronic reconstruction in long-wavelength H-type WS$_{2}$ moir\'e superlattice at nanometer scale. We observe that the long-wavelength WS$_{2}$ moir\'e superlattices experiencing strong atomic reconstruction transform into a hexagonal array of screw dislocations separating large-sized H-stacked domains. Both the geometry and the moir\'e wavelength of the moir\'e superlattice are dramatically tuned by external intralayer heterostrain in our experiment. Remarkably, the STS measurements further demonstrate that the location of the K point in conduction band is modulated sensitively by strain-induced lattice deformation at nanometer scale in this system, with the maximum energy shift reaching up to 300 meV. Our results highlight that intralayer strain plays a vital role in determining structural and electronic properties in TMD moir\'e superlattice.