Plasmonic physics of 2D crystalline materials

TL;DR

This paper investigates the collective electronic excitations in doped 2D materials like graphene, MoS$_2$, and phosphorene using ab initio simulations, revealing material-specific plasmon behaviors and high-energy excitations.

Contribution

It provides a detailed ab initio analysis of plasmonic modes in various 2D materials, emphasizing the importance of realistic dielectric functions for accurate dispersion predictions.

Findings

Different collective modes identified for each material.

High-energy excitations due to interband transitions.

Material-specific dielectric functions are essential for realistic plasmon dispersions.

Abstract

Collective modes of doped two-dimensional crystalline materials, namely graphene, MoS$_2$ and phosphorene, both monolayer and bilayer structures, are explored using the density functional theory simulations together with the random phase approximation. The many-body dielectric functions of the materials are calculated using an {\it ab initio} based model involving material-realistic physical properties. Having calculated the electron energy-loss, we calculate the collective modes of each material considering the in-phase and out-of-phase modes for bilayer structures. Furthermore, owing to many band structures and intreband transitions, we also find high-energy excitations in the systems. We explain that the material-specific dielectric function considering the polarizability of the crystalline material such as MoS$_2$ are needed to obtain realistic plasmon dispersions. For each material studied here, we find different collective modes and describe their physical origins.