Second-harmonic generation from a Ag(111) surface at the interband transition region: Role of the dielectric function

Abstract

The azimuthal-angle dependence and the frequency dependence of second-harmonic generation (SHG) measured at the interband transition region of a Ag(111) surface have been examined using a theoretical model developed by Sipe, Moss, and van Driel [Phys. Rev. B 35, 1129 (1987)]. The analyses of the experimental results provide strong evidence that the dramatic variation of the second-harmonic signal with frequency at 2\ensuremath{\Elzxh}\ensuremath{\omega}=3.87 eV is primarily caused by the sharp change of the dielectric function. The dispersion of the dielectric function affects both the azimuthal angle and the frequency dependence through different radiation efficiencies of the isotropic and anisotropic components of the generated second-harmonic field. The observed SHG features at 3.9 eV can be adequately accounted for by the presence of the interband transitions, and it is not necessary to invoke other surface electronic transitions for their assignments.