S Iwai

Publications (3)7.37 Total impact

• Article: Optical modulation of effective on-site coulomb energy for the Mott transition in an organic dimer insulator.

  Y Kawakami, S Iwai, T Fukatsu, M Miura, N Yoneyama, T Sasaki, N Kobayashi
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  ABSTRACT: We report an optical modulation of the effective on-site Coulomb energy U on a dimer (U_{dimer}) for achieving the Mott insulator-to-metal transition in kappa-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br, as investigated by pump-probe spectroscopy. A reduction of U_{dimer} is optically induced by molecule displacement in the dimer under intradimer excitation. The mechanism of this metallization differs greatly from the photodoping-type mechanism reported previously. In contrast, a faster transition via the photodoping mechanism is detected for interdimer excitation. A metallic-domain-wall oscillation originating from the modulation of U_{dimer} was also observed near the critical end point of the Mott transition line.
  Physical Review Letters 08/2009; 103(6):066403. · 7.37 Impact Factor
• Chapter: Photo-induced macroscopic oscillation between insulator and metal in layered organic Mott insulator

  Y. Kawakami, S. Iwai, N. Yoneyama, T. Sasaki, N. Kobayashi
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  ABSTRACT: Photo-induced insulator to metal transition in two-dimensional organic Mott insulator ĸ-(d-ET)2Cu[N(CN)2]Br was investigated by mid-IR pump-probe spectroscopy. Photo-induced macroscopic GHz oscillation between the Mott insulator and the metal, reflecting the competitive phase diagram, was observed.
  12/2008: pages 176-178;
• Article: Femtosecond mid-IR pump–probe spectroscopy of photoinduced insulator to metal transition in dimer Mott insulator κ-(BEDT-TTF)2X

  Y. Kawakami, H. Nakaya, S. Iwai, N. Yoneyama, T. Sasaki, N. Kobayashi
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  ABSTRACT: Ultrafast dynamics of the photoinduced insulator (I) to metal (M) transition were investigated using femtosecond mid-infrared pump–probe spectroscopy in two-dimensional organic Mott insulators [bis (ethylenedithio)]-tetrathiafulvalene (BEDT-TTF) salts κ-(BEDT-TTF)2X (κ-(ET)2X, where X denotes anion). In κ-(d-ET)2Cu[N(CN)2]Br, a metallic state was photogenerated using a phonon-mediated mechanism: the effective bandwidth increases through the photoinduced molecular rearrangement. The mechanism differs fundamentally from the previously reported photoinduced filling control in one-dimensional Mott insulators.
  Journal of Physics and Chemistry of Solids.