Giant atomic swirl in graphene bilayers with biaxial heterostrain

Abstract

The study of moiré engineering started with the advent of van der Waals heterostructures in which stacking two-dimensional layers with different lattice constants leads to a moiré pattern controlling their electronic properties. The field entered a new era when it was found that adjusting the twist between two graphene layers led to strongly-correlated-electron physics and topological effects associated with atomic relaxation. Twist is now used routinely to adjust the properties of two-dimensional materials. Here, we investigate a new type of moiré superlattice in bilayer graphene when one layer is biaxially strained with respect to the other - so-called biaxial heterostrain. Scanning tunneling microscopy measurements uncover spiraling electronic states associated with a novel symmetry-breaking atomic reconstruction at small biaxial heterostrain. Atomistic calculations using experimental parameters as inputs reveal that a giant atomic swirl forms around regions of aligned stacking to reduce the mechanical energy of the bilayer. Tight-binding calculations performed on the relaxed structure show that the observed electronic states decorate spiraling domain wall solitons as required by topology. This study establishes biaxial heterostrain as an important parameter to be harnessed for the next step of moiré engineering in van der Waals multilayers.

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Cited by in corpus (12)

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• Growth of bilayer stanene on a magnetic topological insulator aided by a buffer layer
• Kagomé quantum oscillations in graphene superlattices
• Structural and electronic signatures of strain-tunable marginally twisted bilayer graphene
• Electronic structure and transport in materials with flat bands: 2D materials and quasicrystals
• Quantifying superlubricity of bilayer graphene from the mobility of interface dislocations
• Geometrical properties of strained and twisted moiré heterostructures
• Twistraintronics in Square Moire Superlattices of Stacked Graphene Layers
• Long wavelength interdomain phonons and instability of dislocations in small-angle twisted bilayers
• Theory for Lattice Relaxation in Marginal Twist Moirés
• Straintronics and twistronics in bilayer graphene
• Interplay of interlayer distance and in-plane lattice relaxations in encapsulated twisted bilayers