Laser-induced ferroelectric structural order in an organic charge-transfer crystal.

Collet, Eric; Lemée-Cailleau, Marie-Hélene; Buron-Le Cointe, Marylise; Cailleau, Hervé; Wulff, Michael; Luty, Tadeusz; Koshihara, Shin-Ya; Meyer, Mathias et al. · Science · 2003

basic_science · Level V

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Abstract

We report the direct observation by x-ray diffraction of a photoinduced paraelectric-to-ferroelectric structural phase transition using monochromatic 100-picosecond synchrotron pulses. It occurs in tetrathiafulvalene-p-chloranil, a charge-transfer molecular material in which electronic and structural changes are strongly coupled. An optical 300-femtosecond laser pulse switches the material from a neutral to an ionic state on a 500-picosecond time scale and, by virtue of intrinsic cooperativity, generates self-organized long-range structural order. The x-ray data indicate a macroscopic ferroelectric reorganization after the laser irradiation. Refinement of the structures before and after laser irradiation indicates structural changes at the molecular level.