Measurement of the optical dielectric function of transition metal   dichalcogenide monolayers: MoS2, MoSe2, WS2 and WSe2
  We report a determination of the complex in-plane dielectric function of monolayers of four transition metal dichalcogenides: MoS2, MoSe2, WS2 and WSe2, for photon energies from 1.5 - 3 eV. The results were obtained from reflection spectra using a Kramers-Kronig constrained variational analysis. From the dielectric functions, we obtain the absolute absorbance of the monolayers. We also provide a comparison of the dielectric function for the monolayers with the corresponding bulk materials. 
Yilei Li, Alexey Chernikov, Xian Zhang, Albert Rigosi, Heather M.   Hill, Arend M. van der Zande, Daniel A. Chenet, En-Min S...
cond-mat.mtrl-sci