Koshihara Okimoto Lab.
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(2) Realistic Examples

Photo-modulation of Ice of Charge in (EDO-TTF)2PF6

Conducting charge transfer complex (EDO-TTF)2PF6 is a quasi-one-dimensional and 3/4-filled electron system and shows metal-insulator phase transition at 280 K due to mixed causes: Peierls instability, charge ordering and anion ordering. Since this material undergoes large structure deformation at the phase transition, not only strong electron correlation but also strong electron-phonon coupling are anticipated in this electron system. Moreover, ultrafast gigantic reflectivity change, which suggests photo-induced insulator-to-metal phase transition, has been recently observed and application to ultrafast photo-switching devices is expected. We have investigated the photo-induced dynamics in this unique material by measuring ultrafast reflectivity change using mid-infrared to visible femtosecond lasers. We found that the photo-induced phase does not simply equal to the thermally induced phase and another phase emerges under high photon-density excitation. Also we found anomaly large amplitude (30 %) of reflectivity oscillation originating from coherent phonon excitation.

Fig.1. Schematics for the charge order pattern in (EDO-TTF)2PF6crystals(left) and change in optical property accompanied with the photo-indiced phase transition in  (EDO-TTF)2PF6 crystals(right) (M. Chollet et al., Science, 307, 86 (2005) and K. Onda et al., Phys. Rev. Lett. 101, 067403 (2008))

Fig.1. Schematics for the charge order pattern in (EDO-TTF)2PF6 crystals(left) and change in optical property accompanied with the photo-indiced phase transition in (EDO-TTF)2PF6 crystals(right) (M. Chollet et al., Science, 307, 86 (2005) and K. Onda et al., Phys. Rev. Lett. 101, 067403 (2008))