Optical coherent current control at surfaces: Theory of injection current

Abstract

We present a study of optical coherent control of injection currents at surfaces of cubic semiconductors, predicting that this new optical effect will serve as a surface-sensitive probe of fundamentally and technologically important crystals with both bulk inversion symmetry (such as cubic diamond $\overline{6}m2$ or $\overline{6}$) and noncentrosymmetric systems (such as zinc-blende symmetry $\overline{4}\overline{3}m$). In crystals with any of these symmetries, this effect vanishes in the bulk, but it is allowed in surface regions due to the breaking of the bulk symmetry there. We present the results of ab initio calculations for injected currents at prototypical clean and Sb-covered GaAs(110)($1\ifmmode\times\else\texttimes\fi{}1$) and clean Si(111)($2\ifmmode\times\else\texttimes\fi{}1$) surfaces, which have well-understood and experimentally reproducible reconstructions. The effects are shown to be essentially sensitive to surface structure, and the injected currents can be interpreted in terms of the surface electronic structure. Calculated magnitudes indicate that the currents should be easily observable, and the calculated spectra of all of the surfaces demonstrate interesting behavior as a function of the energy of the incident light. Finally, layer-by-layer analysis provide detailed access to the surface properties through explicit separation of the contributions coming from different layers.