Ultrafast charge and lattice dynamics in one-dimensional Mott insulator of CuO-chain compoundCa2CuO3investigated by femtosecond absorption spectroscopy

Abstract

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.