Self-consistent dielectric constant determination for monolayer WSe2.

ABSTRACT

Frequency-dependent dielectric constant dispersion of monolayer WSe2, ε(ω)=ε1(ω)+i Îµ2(ω), was obtained from simultaneously measured transmittance and reflectance spectra. Optical transitions of the trion as well as A-, B-, and C-excitons are clearly resolved in the  Îµ2 spectrum. A consistent Kramers-Kronig transformation between the ε1 and  Îµ2 spectra support the validity of the applied analysis. It is found that the A- and B-exciton splitting in the case of the double-layer WSe2 can be attributed to the spin-orbit coupling, which is larger than that in the monolayer WSe2. In addition, the temperature-induced evolution of the A-exciton energy and its width are explained by model equations with electron-phonon interactions.