Infrared nanoscopy of Dirac plasmons at the graphene-SiO2 interface

TL;DR

This study uses infrared nanoscopy to investigate Dirac plasmons in graphene, revealing enhanced interactions with substrate phonons and controllability via gate voltage, advancing understanding of 2D plasmonic phenomena.

Contribution

It demonstrates a novel IR nanoscopy technique to probe high-q Dirac plasmons in graphene and shows their interaction with substrate phonons can be modulated electrically.

Findings

Significant enhancement of in-plane wavevector component q.

Strong interaction between graphene plasmons and SiO2 surface phonons.

Gate voltage effectively controls plasmonic behavior.

Abstract

We report on infrared (IR) nanoscopy of 2D plasmon excitations of Dirac fermions in graphene. This is achieved by confining mid-IR radiation at the apex of a nanoscale tip: an approach yielding two orders of magnitude increase in the value of in-plane component of incident wavevector q compared to free space propagation. At these high wavevectors, the Dirac plasmon is found to dramatically enhance the near-field interaction with mid-IR surface phonons of SiO2 substrate. Our data augmented by detailed modeling establish graphene as a new medium supporting plasmonic effects that can be controlled by gate voltage.