title: Coherent magnetic oscillation in the spin ladder system alpha(')- NaV2O5.
abstract: We report the first observation of coherent magnetic excitations in a spin ladder system NaV2O5 by using femtosecond time-domain spectroscopy. A pronounced coherent oscillation is observed at 127 cm(-1) (nearly twice the spin gap energy) and assigned to a two-magnon bound state, based on the temperature dependence of the intensity below the charge ordering phase transition at T(C) = 34 K. This mode can be observable only when circularly polarized light is used as a pump or a probe beam, suggesting that it corresponds to a spin-flip excitation from the singlet ground state. A phonon mode strongly coupled to the spin state is also found at 303 cm(-1).
authors.affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8581, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kamioka
authors.forename: S
authors.initials: S
authors.lastname: Saito
authors.forename: M
authors.initials: M
authors.lastname: Isobe
authors.forename: Y
authors.initials: Y
authors.lastname: Ueda
authors.forename: T
authors.initials: T
authors.lastname: Suemoto