Ab initio finite-temperature excitons.
The coupling with the lattice vibrations is shown to drastically modify the state-of-the-art picture of the excitonic states based on a frozen-atom approximation. The zero-point vibrations renormalize the bare energies and optical strengths. Excitons acquire a nonradiative lifetime that decreases with increasing temperature. The optical brightness turns out to be strongly temperature-dependent such as to induce bright to dark (and vice versa) transitions. The finite-temperature experimental optical absorption spectra of bulk Si and hexagonal BN are successfully explained without using any external parameter.
Marini
Andrea
A
European Theoretical Spectroscopy Facility (ETSF), CNR-INFM Institute for Statistical Mechanics and Complexity, CNISM, Italy.