J. Phys. IV France 114 (2004) 143
DOI: 10.1051/jp4:2004114034

Ultrafast photo-response in (EDO) ₂PF ₆

Naoki Uchida¹, Shin-ya Koshihara¹, Tadahiko Ishikawa¹, Akira Ota², Souichi Fukaya¹, M. Chollet¹, Hideki Yamochi² and Gunzi Saito<sup>2

1</sup>  Department of Materials Science, Graduate School of Science and Engineering, Tokyo Institute of Technology 2-12-1 Oh-okayama, Meguro-ku, Tokyo 152-8551, Japan
    e-mail: skoshi@cms.titech.ac.jp
²  Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
    e-mail: yamochi@kuchem.kyoto-u.ac.jp

Abstract
Organic conductor (EDO) ₂PF ₆ crystal shows a noble metal (M) insulator (I) transition accompanied with charge ordering, anion ordering and changes in the magnetic character and molecular conformation at T_c= 280 K. This M-I transition can be also sensitively probed by spectroscopic method. Here, we report the reflectivity change in (EDO) ₂PF ₆ crystal induced by the irradiation of weak femto-second (fs) pulsed laser (pulse width: 120 fs) which has been observed utilizing the pump-probe technique. The photo-induced spectral changes strongly suggest the occurrence of the very fast and highly efficient photo-conversion from insulator to metal in the temperature region between 180 K and 270 K. Under certain condition, a half (50%) of the crystal surface was converted into another phase by one excitation photon for every 1000 EDO molecules. Key words. Photo-induced phase transition, insulator to metal, femto-second pulse laser.

© EDP Sciences 2004