Anisotropy and effective medium approach in the optical response of 2D material heterostructures

TL;DR

This paper develops efficient models to describe the optical response of 2D material heterostructures, accounting for anisotropy and structure, validated against ab-initio and classical calculations.

Contribution

It introduces a unified effective medium approach for both vertical and horizontal 2D heterostructures, revealing counter-intuitive isotropic behavior in thin layers.

Findings

Effective models accurately describe optical responses of 2D heterostructures.

Horizontal heterostructures exhibit thickness-dependent optical behavior.

Thin-layer models predict in-plane isotropy despite anisotropic materials.

Abstract

2D materials offer a large variety of optical properties, from transparency to plasmonic excitation. They can be structured and combined to form heterostructures that expand the realm of possibility to manipulate light interactions at the nanoscale. Appropriate and numerically efficient models accounting for the high intrinsic anisotropy of 2D materials and heterostructures are needed. In this article, we retrieve the relevant intrinsic parameters that describe the optical response of a homogeneous 2D material from a microscopic approach. Well-known effective models for vertical heterostructure (stacking of different layers) are retrieved. We found that the effective optical response model of horizontal heterostructures (alternating nano-ribbons) depends of the thickness. In the thin layer model, well adapted for 2D materials, a counter-intuitive in-plane isotropic behavior is predicted. We confront the effective model formulation with exact reference calculations such as ab-initio calculations for graphene, hexagonal boron nitride (hBN), as well as corrugated graphene with larger thickness but also with classical electrodynamics calculations that exactly account for the lateral structuration.