“Excited electronic states: From femto-second dynamics to materials selection”
Electronic excitations and their time evolution are the foundation of how we use and probe materials. Recent experimental advances allow studying this with unprecedented accuracy and even femto-second time resolution, however, interpretation of such experiments requires solid theoretical understanding. An accurate description can be achieved by first-principles theoretical-spectroscopy, based on many-body perturbation and time-dependent density functional theory, and in this talk, I will illustrate recent successful examples: Using these electronic-structure methods we enabled optical crystal-structure identification, provided deep understanding of light absorption for organo-metal halides, and explored the enhancement of defect diffusion by hot electrons under radiation conditions. However, the predictive accuracy of these techniques depends on physical and numerical approximations. I will illustrate our efforts in addressing deficiencies of the description of dielectric screening and explain how we bridge multiple time scales from ultrafast electron dynamics to atomic diffusion. Finally, I will describe how incorporating online databases into computational research on excited electronic states can side-step the problem of high computational cost associated with first-principles simulations, in order to facilitate materials selection for semiconductor heterojunctions.