Excitation-Wavelength-Dependent Charge-Carrier Lifetime in Hematite: An Insight from Nonadiabatic Molecular Dynamics.

Experiments have reported that the photoexcited carrier lifetime in α-Fe 2 O 3 has a significant excitation-wavelength dependence but leave the physical mechanism unresolved. In this work, we rationalize the puzzling excitation-wavelength dependence of the photoexcited carrier dynamics in Fe 2 O 3 by performing nonadiabatic molecular dynamics simulation based on the strongly constrained and appropriately normed functional, which accurately describes the electronic structure of Fe 2 O 3 . Photogenerated electrons with lower-energy excitation relax fast in the t 2g conduction band within about 100 fs, while the photogenerated electrons with higher-energy excitation undergo first a slower interband relaxation from the e g lower state to the t 2g upper state on a time scale of 135 ps, followed by the much faster t 2g intraband relaxation. This study provides insight into the experimentally reported excitation-wavelength dependence of the carrier lifetime in Fe 2 O 3 and a reference for regulating photogenerated carrier dynamics in transition-metal oxides through the light excitation wavelength.