Photoinduced metallic state mediated by spin-charge separation in a one-dimensional organic Mott insulator.

Charge dynamics in a one-dimensional (1D) Mott insulator was investigated by fs pump-probe reflection spectroscopy on an organic charge-transfer compound, bis(ethylenedithio)tetrathiafulvalene-difluorotetracyanoquinodimethane (ET-F2TCNQ). The analyses of the transient reflectivity changes demonstrate that low-energy spectral weight induced by photocarrier doping is concentrated on a Drude component being independent of the doping density, and midgap state is never formed. Such phenomena can be explained by the concept of spin-charge separation characteristic of 1D correlated electron systems.