Ultrafast charge and lattice dynamics in one-dimensional Mott insulator of CuO-chain compound Ca 2 CuO 3 investigated by femtosecond absorption spectroscopy

Charge dynamics in one-dimensional (1D) Mott insulators was investigated by femtosecond pump-probe absorption spectroscopy on ${\\mathrm{Ca}}_{2}{\\mathrm{CuO}}_{3}$. An irradiation of a femtosecond laser pulse gives rise to a Drude-like response due to the nature of spin-charge separation characteristic of 1D Mott insulators. The photoinduced metallic state decays with \\ensuremath{\\sim}30 fs, and photocarriers are localized as polarons via charge-phonon coupling which produce a broad midgap absorption. Calculations with the extended Hubbard-Holstein model suggest that the peak structure of the midgap absorption is a magnon sideband of the polaron absorption. This demonstrates that charge-spin coupling becomes effective via charge-phonon coupling in polarons.