Rotational and dilational reconstruction in transition metal dichalcogenide moiré bilayers

Madeline Van Winkle; Isaac M Craig; Stephen Carr; Medha Dandu; Karen C Bustillo; Jim Ciston; Colin Ophus; Takashi Taniguchi; Kenji Watanabe; Archana Raja; Sinéad M Griffin; D Kwabena Bediako

doi:10.1038/s41467-023-38504-7

Rotational and dilational reconstruction in transition metal dichalcogenide moiré bilayers

Nat Commun. 2023 May 24;14(1):2989. doi: 10.1038/s41467-023-38504-7.

Authors

Madeline Van Winkle^#¹, Isaac M Craig^#^{1

2

3}, Stephen Carr^{4

5}, Medha Dandu², Karen C Bustillo², Jim Ciston², Colin Ophus², Takashi Taniguchi⁶, Kenji Watanabe⁷, Archana Raja², Sinéad M Griffin^{2

3}, D Kwabena Bediako^{8

9}

Affiliations

¹ Department of Chemistry, University of California, Berkeley, CA, 94720, USA.
² Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
³ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁴ Department of Physics, Brown University, Providence, RI, 02912, USA.
⁵ Brown Theoretical Physics Center, Brown University, Providence, RI, 02912, USA.
⁶ International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
⁷ Research for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
⁸ Department of Chemistry, University of California, Berkeley, CA, 94720, USA. bediako@berkeley.edu.
⁹ Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. bediako@berkeley.edu.

^# Contributed equally.

Abstract

Lattice reconstruction and corresponding strain accumulation plays 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 by 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.

Abstract

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