Time-dependent exciton wave functions from TDDFT*

Time-dependent density-functional theory (TDDFT) is a computationally efficient alternative to the Bethe-Salpeter equation for calculating optical spectra in insulators and semiconductors, including excitonic effects. We show how time-dependent exciton wave functions can be obtained from TDDFT via the time-dependent Kohn-Sham transition density matrix. The method is illustrated using one-dimensional model solids.