Ultrafast many-body bright-dark exciton transition in anatase TiO<sub>2</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37956295.
- Also identified by DOI 10.1073/pnas.2307671120 and PMC identifier 10666115.
- Licence recorded as CC BY-NC-ND.
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Abstract
The momentum-forbidden dark excitons can have a pivotal role in quantum information processing, Bose-Einstein condensation, and light-energy harvesting. Anatase TiO<sub>2</sub> with an indirect band gap is a prototypical platform to study bright to momentum-forbidden dark exciton transition. Here, we examine, by GW plus the real-time Bethe-Salpeter equation combined with the nonadiabatic molecular dynamics (GW + rtBSE-NAMD), the many-body transition that occurs within 100 fs from the optically excited bright to the strongly bound momentum-forbidden dark excitons in anatase TiO<sub>2</sub>. Comparing with the single-particle picture in which the exciton transition is considered to occur through electron-phonon scattering, within the GW + rtBSE-NAMD framework, the many-body electron-hole Coulomb interaction activates additional exciton relaxation channels to notably accelerate the exciton transition in competition with other radiative and nonradiative processes. The existence of dark excitons and ultrafast bright-dark exciton transitions sheds insights into applications of anatase TiO<sub>2</sub> in optoelectronic devices and light-energy harvesting as well as the formation process of dark excitons in semiconductors.