Surface susceptibility and conductivity of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>WSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> monolayers: A first-principles and ellipsometry characterization
Joshua D. Elliott, Zhemi Xu, Paolo Umari, Gaurav Jayaswal, Mingguang Chen, Xixiang Zhang, Alessandro Martucci, Margherita Marsili, Michele Merano
Abstract
We employ a recent formulation for the optical properties of two-dimensional crystals from first principles [L. Matthes et al., New J. Phys. 16, 105007 (2014); L. Matthes et al., Phys. Rev. B 94, 205408 (2016)] to compute the surface susceptibility and surface conductivity of ${\mathrm{MoS}}_{2}$ and ${\mathrm{WSe}}_{2}$ monolayers [G. Jayaswal et al., Opt. Lett. 43, 703 (2018)]. As electron-hole interactions are known to be crucial for the description of the absorption spectrum of monolayer transition metal dichalcogenides, the excitonic dielectric function is computed at the Bethe-Salpeter equation level, including spin-orbit interactions. For both of these examples, excellent agreement with experimental ellipsometry measurements is obtained. Driven by the emergence of additional features in our theoretical results, we applied a second-derivative analysis in order to identify excited exciton peaks in the ellipsometric spectra.