Nonlinear Optical Properties of Transition-Metal Dichalcogenide MX<inf>2</inf> (M = Mo, W; X = S, Se) Monolayers and Trilayers from First-Principles Calculations
Journal
Journal of Physical Chemistry C
Journal Volume
119
Journal Issue
23
Pages
13268-13276
Date Issued
2015
Author(s)
Wang, C.-Y.
Abstract
Because of the absence of interlayer coupling and inversion symmetry, transition-metal dichalcogenide (MX2) semiconductor monolayers exhibit novel properties that are distinctly different from their bulk crystals such as direct optical band gaps, large band spin splittings, spin-valley coupling, and piezoelectric and nonlinear optical responses and thus have promising applications in, for example, optoelectronic and spintronic devices. Here, we have performed a systematic first-principles study of the second-order nonlinear optical properties of MX2 (M = Mo, W; X = S, Se) monolayers and trilayers within the density functional theory with the generalized gradient approximation plus scissors correction. We find that all the four MX2 monolayers possess large second-order optical susceptibility χ(2) in the optical frequency range and significant linear electro-optical coefficients in the low-frequency limit, thus indicating their potential applications in nonlinear optical devices and electric optical switches. The χ(2) spectra of the MX2 trilayers are overall similar to the corresponding MX2 monolayers, albeit with the magnitude reduced by roughly a factor of 3. The prominent features in the χ(2) spectra of the MX2 multilayers are analyzed in terms of the underlying band structures and optical dielectric function and are also compared with available experiments.
Type
journal article