Direct Imaging Strain-field Vortex Networks in Twisted Bilayer Graphene Magnified by Moir\'e Superlattices

TL;DR

This study demonstrates a method to directly image and analyze strain-field vortex networks in twisted bilayer graphene by magnifying atomic-scale distortions using a topmost graphene moiré pattern, revealing insights into atomic reconstruction effects.

Contribution

The paper introduces a novel imaging technique that magnifies tiny lattice rotations in twisted bilayer graphene, enabling direct visualization of strain-field vortex networks.

Findings

Magnified sub-Angstrom lattice distortions using topmost graphene moiré patterns.

Real-space imaging of strain-field vortex networks in twisted bilayer graphene.

Atomic-scale reconstruction influences the electronic properties of vdW heterostructures.

Abstract

In two-dimensional (2D) twisted bilayers, the van der Waals (vdW) interlayer interaction introduces atomic-scale reconstruction at interface by locally rotating lattice to form strain-field vortex networks in their moir\'e superlattice. However, direct imaging the tiny local lattice rotation of the strain-field vortex requires extremely high spatial resolution and is an outstanding challenge in experiment. Here, a topmost small-period graphene moir\'e pattern is introduced to magnify sub-Angstrom distortions of the lattice and tiny local lattice rotation in underlying twisted bilayer graphene (TBG). The local periods and low-energy van Hove singularities of the topmost graphene moir\'e patterns are spatially modified by the atomic-scale reconstruction of the underlying TBG, thus enabling real-space imaging of the strain-field vortex networks. Our results indicate that structure-reconstructed vdW systems can provide a unique substrate to spatially engineer supported two-dimensional materials both in structures and electronic properties.