|approved||summary.pdf||2015-04-07 13:05:46||Sean Anderson|
Author: Sean M. Anderson
Requested Type: Poster
Submitted: 2015-03-12 14:15:37
Co-authors: N.Tancogne-Dejean, B.S. Mendoza, V.Véniard
Centro de Investigaciones en Optica, A.C.
Loma del Bosque 115
Leon, Guanajuato 37150
We formulate a theoretical approach of surface second-harmonic generation from semiconductor surfaces based on the length gauge and the electron density operator within the independent particle approximation. We calculate the nonlinear second-order surface susceptibility tensor including the scissors correction (needed to have the correct value of the energy band gap), the contribution from the nonlocal part of the pseudopotentials (routinely used in ab initio band-structure calculations), and the derivation for the inclusion of the cut function (used to extract the surface response). The first two contributions are described by spatially nonlocal quantum-mechanical operators and are fully taken into account in the present formulation. We evaluate the calculation on the clean Si(001)2x1 reconstructed surface. The scissors correction shifts the spectrum to higher energies though the shifting is not rigid and mixes the omega and two-omega resonances and has a strong influence on the line shape. The effects of the nonlocal part of the pseudopotentials preserves the line shape but reduces its value by 15%-20%. The inclusion of these three contributions is very important and makes our scheme unprecedented and opens the possibility to study surface second-harmonic generation with more versatility while providing more accurate results.