Probing the Ultimate Plasmon Confinement Limits with a Van der Waals heterostructure

TL;DR

This paper demonstrates that a graphene-insulator-metal heterostructure can confine plasmons to a length scale of a single atom, surpassing traditional limits imposed by metal losses, enabling new ultra-strong light-matter interaction regimes.

Contribution

It introduces a novel heterostructure design that achieves atomic-scale plasmon confinement, overcoming the Landau damping trade-off in metals.

Findings

Plasmons confined to atomic scale in heterostructure

Far-field excitation of ultra-confined plasmons demonstrated

Theoretical model accounts for non-local optical responses

Abstract

The ability to confine light into tiny spatial dimensions is important for applications such as microscopy, sensing and nanoscale lasers. While plasmons offer an appealing avenue to confine light, Landau damping in metals imposes a trade-off between optical field confinement and losses. We show that a graphene-insulator-metal heterostructure can overcome that trade-off, and demonstrate plasmon confinement down to the ultimate limit of the lengthscale of one atom. This is achieved by far-field excitation of plasmon modes squeezed into an atomically thin hexagonal boron nitride dielectric h-BN spacer between graphene and metal rods. A theoretical model which takes into account the non-local optical response of both graphene and metal is used to describe the results. These ultra-confined plasmonic modes, addressed with far-field light excitation, enables a route to new regimes of ultra-strong light-matter interactions.