URL:http://link.aps.org/doi/10.1103/PhysRevB.79.233201
DOI:10.1103/PhysRevB.79.233201Optical processes in insulators and semiconductors, including excitonic effects, can be described in principle exactly using time-dependent density-functional theory (TDDFT). Starting from a linearization of the TDDFT semiconductor Bloch equations in a two-band model, we derive a simple formalism for calculating exciton binding energies. This formalism leads to a generalization of the standard Wannier equation for excitons, featuring a nonlocal effective electron-hole interaction determined by long-range and dynamical exchange-correlation (XC) effects. We calculate exciton binding energies in several direct-gap semiconductors using exchange-only and model XC kernels.This work was supported by Research Corporation and by NSF under Grant No. DMR-0553485. We thank Angel Rubio, Lucia Reining, and Claudia Ambrosch-Draxl for useful discussions
