Abstract
We compute from first principles the infrared dispersion of the nonlinear susceptibility in zinc-blende semiconductors. At terahertz frequencies the nonlinear susceptibility depends not only on the purely electronic response , but also on three other parameters , , and describing the contributions from ionic motion. They relate to the TO Raman polarizability, the second-order displacement-induced dielectric polarization, and the third-order lattice potential. Contrary to previous theory, we find that mechanical anharmonicity dominates over electrical anharmonicity , which is consistent with recent experiments on GaAs. We predict that the sharp minimum in the intensity of second-harmonic generation recently observed for GaAs between and does not occur for several other III-V compounds.
- Received 29 August 2006
DOI:https://doi.org/10.1103/PhysRevB.74.245204
©2006 American Physical Society