Nonlinear optical responses in hydrogenated graphene structures (Phys. Status Solidi B 2/2016)

Abstract

The upper left (u.l.) panel represents the 50% hydrogenated graphene structure C16H8-up, which upon the incidence of a circularly polarized light beam (in red) creates spin-polarized electrons in the conduction bands. The degree of spin polarization along the three Cartesian directions i = x,y,z (see upper right diagram) can reach more than 50% for , as represented by the solid black arrows pointing down in the u.l. image. The same beam can induce an electronic injection current, as shown by the thick black arrow in the u.l. sketch. According to the calculations by Zapata-Peña et al. (pp. 226–233), the most intense component of the injection current tensor is , which goes along the plane of the structure, where the middle right panel shows the decomposition of the current into each layer contribution. The diagram bottom left shows the nonlinear susceptibility component , responsible for second harmonic generation (SHG), which is found to be almost 1000 times bigger than that of GaAs. The image bottom right depicts the fact that, as the structure is highly noncentrosymmetric since H atoms are only on one side, the nonlinear response is very large.