  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.
