Photoexcitation of the one-dimensional extended Peierls–Hubbard model at quarter-filling

Utilizing the time-dependent Lanczos method, we investigate the photoexcitation dynamics of the one-dimensional (1D) extended Peierls–Hubbard model at quarter filling. In equilibrium, it is well established that introducing the nearest-neighbour interaction V into the 1D Peierls–Hubbard model can lead to the formation of Mott–Hubbard excitons, which exhibit a characteristic frequency in the optical conductivity that is lower than the Mott gap. Ultrafast photoexcitation of this model gives rise to a transient metallic state for V < 2, characterized by several features, including a zero-frequency Drude peak in the post-pump optical conductivity, an increase in the density of charge carriers, and enhanced electron hopping between dimers. In contrast, when V ≥ 2, this metallic state is no longer observed, as photoinduced carriers bind to form excitons, thereby inhibiting metallic behavior. These results highlight a parallel between the optical excitation of the 1D extended Peierls–Hubbard model at quarter filling and that of the 1D extended Hubbard model at half filling, suggesting a universal mechanism governing their photoinduced responses.