Rotational and Dilational Reconstruction in Transition Metal Dichalcogenide Moiré Bilayers

Abstract

Lattice reconstruction and corresponding strain accumulation play a key role in defining the electronic structure of two-dimensional moiré superlattices, including those of transition metal dichalcogenides (TMDs). Imaging of TMD moirés has so far provided a qualitative understanding of this relaxation process in terms of interlayer stacking energy, while models of the underlying deformation mechanisms have relied on simulations. Here, we use interferometric four-dimensional scanning transmission electron microscopy to quantitatively map the mechanical deformations through which reconstruction occurs in small-angle twisted bilayer MoS2 and WSe2/MoS2 heterobilayers. We provide direct evidence that local rotations govern relaxation for twisted homobilayers, while local dilations are prominent in heterobilayers possessing a sufficiently large lattice mismatch. Encapsulation of the moiré layers in hBN further localizes and enhances these in-plane reconstruction pathways, suppressing out-of-plane corrugation. We also find that extrinsic uniaxial heterostrain, which introduces a lattice constant difference in twisted homobilayers, leads to accumulation and redistribution of reconstruction strain, demonstrating another route to modify the moiré potential.

27 pages, 5 figures

References in corpus (6)

• scikit-image: Image processing in Python
• Observation of Moiré Excitons in WSe2/WS2 Heterostructure Superlattices
• Resonantly hybridised excitons in moiré superlattices in van der Waals heterostructures
• Hyperspectral imaging of excitons within a moiré unit-cell with a sub-nanometer electron probe
• Rotational and Dilational Reconstruction in Transition Metal Dichalcogenide Moiré Bilayers
• Torsional Periodic Lattice Distortions and Diffraction of Twisted 2D Materials

Cited by in corpus (15)

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• Local atomic stacking and symmetry in twisted graphene trilayers
• A room-temperature moiré interlayer exciton laser
• Impact of atomic reconstruction on optical spectra of twisted TMD homobilayers
• Nano-optics of transition metal dichalcogenides and their van der Waals heterostructures with electron spectroscopies
• Evolution of flat bands in MoSe${}_2$/WSe${}_2$ moiré lattices: A study combining machine learning and band unfolding methods
• Influence of atomic relaxations on the moiré flat band wavefunctions in antiparallel twisted bilayer WS${}_{\text{2}}$
• Polarization and charge-separation of moiré excitons in van der Waals heterostructures
• Moiré Superstructures in Marginally-Twisted NbSe${}_2$ Bilayers
• Considerations for extracting moiré-level strain from dark field intensities in transmission electron microscopy
• Strong atomic reconstruction in twisted bilayers of highly flexible InSe: Machine-Learned Interatomic Potential and continuum model approaches
• Review of the tight-binding method applicable to the properties of moiré superlattices
• Moire-Engineered Excitonic Landscape and Phonon-Mediated Recombination in Twisted WSe2 Bilayers