Giant Atomic Swirl in Graphene Bilayers with Biaxial Heterostrain

We report a new type of moiré superlattice in bilayer graphene. The superlattice does not originate from twist between the layers but from biaxial heterostrain. Here one layer is strained with respect to the other. In our experimental implementation biaxial heterostrain is small (~0.1%) and the superlattice is huge ~250 nm in period so that the system relaxes to a more favourable configuration where strain is confined in narrow spiraling 1D regions hosting topological electronic states. Graphene bilayers with biaxial heterostrain therefore offers a new playground for moiré physics in graphene.
Référence : Advanced Materials