Ultrasensitive acoustic graphene plasmons in a graphene-transition metal dichalcogenide heterostructure: strong plasmon-phonon coupling and wavelength sensitivity enhanced by a metal screen

TL;DR

This study demonstrates that using a metal substrate in graphene-TMD heterostructures significantly enhances plasmon-phonon coupling and wavelength sensitivity, enabling high-resolution probing of heterostructure details through acoustic plasmons.

Contribution

The paper introduces a quantum electrostatic heterostructure model showing that metal substrates boost coupling strength and sensitivity of acoustic graphene plasmons in heterostructures.

Findings

Enhanced plasmon-phonon coupling with metal substrate

Improved wavelength sensitivity to structural details

Potential for monolayer resolution in structural probing

Abstract

Acoustic plasmons in graphene exhibit strong confinement induced by a proximate metal surface and hybridize with phonons of transition metal dichalcogenides (TMDs) when these materials are combined in a van der Waals heterostructure, thus forming screened graphene plasmon-phonon polaritons (SGPPPs), a type of acoustic mode. While SGPPPs are shown to be very sensitive to the dielectric properties of the environment, enhancing the SGPPPs coupling strength in realistic heterostructures is still challenging. Here we employ the quantum electrostatic heterostructure model, which builds upon the density functional theory calculations for monolayers, to show that the use of a metal as a substrate for graphene-TMD heterostructures (i) vigorously enhances the coupling strength between acoustic plasmons and the TMD phonons, and (ii) markedly improves the sensitivity of the plasmon wavelength on the structural details of the host platform in real space, thus allowing one to use the effect of environmental screening on acoustic plasmons to probe the structure and composition of a van der Waals heterostructure down to the monolayer resolution.