Plasmons in MoS2 studied via experimental and theoretical correlation of energy loss spectra

This paper takes a fundamental view of the electron energy loss spectra of monolayer and few layer MoS2. The dielectric function of monolayer MoS2 is compared to the experimental spectra to give clear criteria for the nature of different signals. Kramers-Krönig analysis allows a direct extraction of the dielectric function from the experimental data. However this analysis is sensitive to slight changes in the normalisation step of the data pre-treatment. Density functional theory provides simulations of the dielectric function for comparison and validation of experimental findings. Simulated and experimental spectra are compared to isolate the 𝜋 and 𝜋 +𝜎 surface plasmon modes in monolayer MoS2. Singleparticle excitations obscure the plasmons in the monolayer spectrum and momentum resolved measurements give indication of indirect interband transitions that are excited due to the large convergence and collection angles used in the experiment.