First-principles study of ultrafast bandgap dynamics in laser-excited α -quartz

Femtosecond-laser-induced evolution of α -quartz bandgap was calculated using first principles. First, time-dependent density functional theory (TDDFT) was used to describe excited electron dynamics during the laser pulse irradiation. Then, the temperature of excited electrons was estimated using finite-temperature DFT. Finally, the GW approximation was applied to calculate the electronic structure modification driven by hot electrons. As a result, an ultrafast decrease of the bandgap is observed during a 15-fs laser pulse with a drop of 35