Probing the structure and composition of van der Waals heterostructures using the nonlocality of Dirac plasmons in the terahertz regime

TL;DR

This paper demonstrates that the nonlocal properties of Dirac plasmons in graphene can be used to probe the detailed structure and composition of van der Waals heterostructures, achieving high resolution and compositional insights.

Contribution

It introduces a method to analyze vdW heterostructures using Dirac plasmon nonlocality, enabling layer-specific and compositional characterization in the terahertz regime.

Findings

Single-layer resolution of vdWh composition via plasmon nonlocality.

Plasmon-phonon coupling reveals multilayer TMD stack composition.

Bulk plasmonic screening properties emerge beyond 100 TMD layers.

Abstract

Dirac plasmons in graphene are very sensitive to the dielectric properties of the environment. We show that this can be used to probe the structure and composition of van der Waals heterostructures (vdWh) put underneath a single graphene layer. In order to do so, we assess vdWh composed of hexagonal boron nitride and different types of transition metal dichalcogenides (TMDs). By performing realistic simulations that account for the contribution of each layer of the vdWh separately and including the importance of the substrate phonons, we show that one can achieve single-layer resolution by investigating the nonlocal nature of the Dirac plasmon-polaritons. The composition of the vdWh stack can be inferred from the plasmon-phonon coupling once it is composed by more than two TMD layers. Furthermore, we show that the bulk character of TMD stacks for plasmonic screening properties in the terahertz regime is reached only beyond 100 layers.