Tetrahedral Bonding in Twisted Bilayer Graphene by Carbon Intercalation

TL;DR

This study uses ab initio calculations to reveal that intercalating twisted bilayer graphene with carbon can locally induce tetrahedral bonding, pulling layers closer and offering new ways to manipulate layered heterostructures.

Contribution

It demonstrates a novel effect of carbon intercalation in twisted bilayer graphene, enabling local layer bonding changes not seen in AB or AA stacking.

Findings

Carbon intercalation pulls layers closer in certain regions.

Tetrahedral bonding forms between intercalant and layer atoms.

Effect is specific to twisted bilayer graphene with carbon.

Abstract

Based on ab initio calculations, we study the effect of intercalating twisted bilayer graphene with carbon. Surprisingly, we find that the intercalant pulls the atoms in the two layers closer together locally when placed in certain regions in between the layers, and the process is energetically favorable as well. This arises because in these regions of the supercell, the local environment allows the intercalant to form tetrahedral bonding with nearest atoms in the layers. Intercalating AB- or AA-bilayer graphene with carbon does not produce this effect; therefore, the nontrivial effect owes its origin to both using carbon as an intercalant and using twisted bilayer graphene as the host. This opens new routes to manipulating bilayer and multilayer van der Waals heterostructures and tuning their properties in an unconventional way.