Ultrafast Charge Dynamics in One-Dimensional Organic Mott Insulators

Abstract

Ultrafast charge dynamics in one-dimensional Mott insulators was investigated by femtosecond reflection spectroscopy on three organic molecular compounds, K–tetracyanoquinodimethane (TCNQ), Rb–TCNQ, and bis(ethylenedithio)tetrathiafulvalene (ET)–difluorotetracyanoquinodimethane (F₂TCNQ) with different magnitudes of electron–lattice (e–l) interaction. In K– and Rb–TCNQ, photocarriers are localized as polarons with ∼70 fs and recombine with a few ps. In ET–F₂TCNQ, photocarriers lead to a metallic state and decay with ∼200 fs. Such differences of the charge dynamics are reasonably interpreted by taking into account the magnitudes of the e–l interactions.