Photonic crystals for nano-light in moir\'e graphene superlattices

TL;DR

This paper demonstrates that twisted bilayer graphene forms a natural plasmonic photonic crystal at small twist angles, enabling control of nano-light without complex nanofabrication, by exploiting quantum properties of layered materials.

Contribution

It reveals that atomic reconstruction in twisted bilayer graphene creates a natural plasmonic crystal, a novel phenomenon not previously reported.

Findings

Atomic reconstruction at small twist angles transforms TBG into a plasmonic crystal.

Infrared nano-imaging shows controlled propagation of nano-light in TBG.

Potential for controlling nano-light using quantum properties of layered materials.

Abstract

Graphene is an atomically thin plasmonic medium that supports highly confined plasmon polaritons, or nano-light, with very low loss. Electronic properties of graphene can be drastically altered when it is laid upon another graphene layer, resulting in a moir\'e superlattice. The relative twist angle between the two layers is a key tuning parameter of the interlayer coupling in thus obtained twisted bilayer graphene (TBG). We studied propagation of plasmon polaritons in TBG by infrared nano-imaging. We discovered that the atomic reconstruction occurring at small twist angles transforms the TBG into a natural plasmon photonic crystal for propagating nano-light. This discovery points to a pathway towards controlling nano-light by exploiting quantum properties of graphene and other atomically layered van der Waals materials eliminating need for arduous top-down nanofabrication.