Improvedab initiocalculation of surface second-harmonic generation from Si(111)(1×1):H

Abstract

We carry out an improved ab initio calculation of surface second-harmonic generation (SSHG) from the Si(111)(1×1):H surface. This calculation includes three new features in one formulation: (i) the scissors correction, (ii) the contribution of the nonlocal part of the pseudopotentials, and (iii) the inclusion of a cut function to extract the surface response, all within the independent particle approximation. We apply these improvements on the Si(111)(1×1):H surface and compare with various experimental spectra from several different sources. We also revisit the three-layer model for the SSHG yield and demonstrate that it provides more accurate results over several, more common, two-layer models. We demonstrate the importance of using properly relaxed coordinates for the theoretical calculations. We conclude that this approach to the calculation of the second-harmonic spectra is versatile and accurate within this level of approximation. This well-characterized surface offers an excellent platform for comparison with theory and allows us to offer this study as an efficient benchmark for this type of calculation.

Nonlinear optical susceptibility of atomically thin WX2 crystals

“…The fitting curves are obtained for two different bandgap parameters. The solid green line in Figure 10 [36][37][38][39]. We believe that our experimental data are valuable for developing and refining the rigorous theoretical approaches to simulate optical nonlinearities in systems with quantum confinement.…”