Analogy and dissimilarity of excitons in monolayer and bilayer of MoSe₂

Abstract Excitons in thin layers of semiconducting transition metal dichalcogenides are highly subject to the strongly modified Coulomb electron-hole interaction in these materials. Therefore, they do not follow the model system of a two-dimensional hydrogen atom. We investigate experimentally and theoretically excitonic properties in both the monolayer (ML) and the bilayer (BL) of MoSe 2 encapsulated in hexagonal BN. The measured magnetic field evolutions of the reflectance contrast spectra of the MoSe 2 ML and BL allow us to determine g -factors of intralayer A and B excitons, as well as the g -factors of the interlayer exciton. We explain the dependence of g -factors on the number of layers and excitation state can be explained using first principles calculations. Furthermore, we demonstrate that the experimentally measured ladder of excitonic s states in the ML can be reproduced using the k·p approach with the Rytova-Keldysh potential that describes the electron-hole interaction. In contrast, the analogous calculation for the BL case require taking into account the out-of-plane dielectric response of the MoSe 2 BL.