Investigation of the dispersion and the effective masses of excitons in bulk 2H-MoS2 using transition electron energy-loss spectroscopy

TL;DR

This study uses electron energy-loss spectroscopy to analyze exciton dispersion and effective masses in bulk 2H-MoS2, revealing anisotropic quadratic dispersion and close agreement with theoretical predictions.

Contribution

It provides detailed experimental measurements of exciton dispersion and effective masses in bulk 2H-MoS2, enhancing understanding of its electronic excitations.

Findings

Exciton dispersions are approximately quadratic with slight anisotropy.

Effective masses of excitons closely match theoretical predictions.

Identified A1 and B1 exciton peaks in energy-momentum spectra.

Abstract

We have investigated the electronic excitations in bulk 2H-MoS2 using electron energy-loss spectroscopy. The electron energy-loss spectra in the {\Gamma}M and {\Gamma}K directions were measured for various momentum transfer values. The results allow the identification of the A1 and B1 exciton peaks and in particular their energy-momentum dispersion. The dispersions exhibit approximately quadratic upward trends and slight anisotropies in the {\Gamma}M and {\Gamma}K directions. The fitted energy-momentum transfer functions allow the estimation of the effective masses of the excitons which are in close proximity to predicted values.