Measuring local moiré lattice heterogeneity of twisted bilayer graphene

Abstract

We introduce a new method to continuously map inhomogeneities of a moiré lattice and apply it to large-area topographic images we measure on open-device twisted bilayer graphene (TBG). We show that the variation in the twist angle of a TBG device, which is frequently conjectured to be the reason for differences between devices with a supposed similar twist angle, is about 0.08° around the average of 2.02° over areas of several hundred nm, comparable to devices encapsulated between hBN slabs. We distinguish between an effective twist angle and local anisotropy and relate the latter to heterostrain. Our results imply that for our devices, twist angle heterogeneity has a roughly equal effect to the electronic structure as local strain. The method introduced here is applicable to results from different imaging techniques, and on different moiré materials.

4 figures in main text. Supporting info included

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• Symmetric Kondo Lattice States in Doped Strained Twisted Bilayer Graphene
• Continuum effective Hamiltonian for graphene bilayers for an arbitrary smooth lattice deformation from microscopic theories
• Dynamical correlations and order in magic-angle twisted bilayer graphene
• Degradation of phonons in disordered moiré superlattices
• Stacking domain morphology in epitaxial graphene on silicon carbide
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• Twistraintronics in Square Moire Superlattices of Stacked Graphene Layers
• Low-Energy Electron Microscopy contrast of stacking boundaries: comparing twisted few-layer graphene and strained epitaxial graphene on silicon carbide
• Delusive chirality and periodic strain pattern in moiré systems