# Plasmon modes of bilayer molybdenum disulfide: A density functional study

## TL;DR

This study uses density functional theory and the random phase approximation to investigate plasmon modes in bilayer MoS2, revealing three distinct collective electronic excitations sensitive to doping levels.

## Contribution

It provides a detailed ab initio analysis of plasmon modes in bilayer MoS2, including the prediction of three specific plasmon excitations and their dependence on doping.

## Key findings

- Identification of three plasmon modes in bilayer MoS2
- Doping significantly affects the electron energy-loss spectra
- Prediction of a $
oot q$ dispersion for the optical mode

## Abstract

We explore the collective electronic excitations of bilayer molybdenum disulfide (MoS$_2$) using the density functional theory together with the random phase approximation. The many-body dielectric function and electron energy-loss spectra are calculated using an {\it ab initio} based model involving material-realistic physical properties. The electron energy-loss function of bilayer MoS$_2$ system is found to be sensitive to either electron or hole doping and it is owing to the fact that the Kohn-Sham band dispersions are not symmetric for energies above and below the zero Fermi level. Three plasmon modes are predicted. A damped high-energy mode, one optical mode (in-phase mode) for which the plasmon dispersion exhibits $\sqrt q $ in the long wavelength limit originating from low-energy electron scattering and finally a highly damped acoustic mode (out-of-phase mode).