title: Collective excitation of an electric dipole on a molecular dimer in an organic dimer-Mott insulator.
abstract: The terahertz response in 10-100 cm(-1) was investigated in an organic dimer-Mott (DM) insulator κ-(ET)(2)Cu(2)(CN)(3) that exhibits a relaxorlike dielectric anomaly. An ~30 cm(-1) band in the optical conductivity was attributable to collective excitation of the fluctuating intradimer electric dipoles that are formed by an electron correlation. We succeeded in observing photoinduced enhancement of this ~30 cm(-1) band, reflecting the growth of the electric dipole cluster in the DM phase. Such optical responses in κ-(ET)(2)Cu(2)(CN)(3) reflect an instability near the boundary between the DM-ferroelectric charge ordered phases.
authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Itoh
authors.forename: H
authors.initials: H
authors.lastname: Itoh
authors.forename: M
authors.initials: M
authors.lastname: Naka
authors.forename: S
authors.initials: S
authors.lastname: Saito
authors.forename: I
authors.initials: I
authors.lastname: Hosako
authors.forename: N
authors.initials: N
authors.lastname: Yoneyama
authors.forename: S
authors.initials: S
authors.lastname: Ishihara
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.forename: S
authors.initials: S
authors.lastname: Iwai