Photo-induced dynamics of Pt(dmit)2 salts studied by optical spectroscopy and electron-diffraction technique

ISHIKAWA, T.; ONDA, K.; OKIMOTO, Y.; KOSHIHARA, S.; HAYES, S. A. ; KESKIN, S.; CORTHEY, G.; HADA, M.; PICHUGIN, K.; MARX, A.; MILLER, R. J. D.; MOREAC, A.; KAZUB, W.; LORENC, M.; YAMAMOTO, T.; NOMURA, M.; KATO, R.

Congreso; 5th International Conference on Photoinduced Phase Transitions and Cooperative Phenomena (PIPT5-); 2014

M(dmit)2 (M=Pd, Pt) salts show an unique phase transition due to the strong electron-phonon and electron-electron correlations [1]. We reported the optical spectral change induced by the photoexcitation in the charge separated (CS) phase of the Et2Me2Sb[Pd(dmit)2]2 single crystal, which suggests the occurrence of the photoinduced phase transition (PIPT) [2]. Recently, A[Pt(dmit)2]2 (A=Me4P, Me4As and Me4Sb) are crystalized and studied by transport and X-ray crystallographic technique [3]. The Pt(dmit)2 system also shows the CS phase with relatively higher transition temperature up to 215 K thanks to the relatively weaker dimerization of the Pt(dmit)2 than Pd(dmit)2 molecules. To investigate the photoinduced phenomena in this Pt(dmit)2 salt is interesting for application, because of its high transition temperature, as well as unveiling the mechanism of phase transition based on CS mechanism by virtue of the freedom of molecular orbitals. Since, the dimerization, the distance between the molecules, plays a key role in determining the electronic structure of the Pt(dmit)2 salt, the direct observation of the photoinduced lattice structural change must be the powerful technique to study the dynamics of PIPT. Using the recent developed time-resolved electron diffraction technique [4], we have succeeded in observing directly the photoinduced lattice structural change with ps time scale from the CS phase and also clear coherent oscillation of the intensity of the Bragg peaks with the frequency of THz scale in the photoinduced state. By comparing the results of time-resolved optical spectroscopy and electron diffraction pattern, we are trying to clarify the precise photoinduced dynamics of PIPT in this material.References: [1] M. Tamura and R. Kato, Sci. Technol. Adv. Mater. 10, 024304 (2009).[2] T. Ishikawa, N. Fukazawa, Y. Matsubara, R. Nakajima, K. Onda, Y. Okimoto, S. Koshihara, M. Lorenc, E. Collet, M. Tamura, and R. Kato, Phys. Rev. B 80, 115108 (2009).[3] M. Nomura, A. Tajima, H.-B. Cui, M. A. Jawad, T. Tsumuraya, Y. Oshima, T. Miyazaki, and R. Kato, in ICSM2012 (2012).[4] M. Gao, C. Lu, H. Jean-Ruel, L. C. Liu, A. Marx, K. Onda, S.-Y. Koshihara, Y. Nakano, X. Shao, T. Hiramatsu, G. Saito, H. Yamochi, R. R. Cooney, G. Moriena, G. Sciaini, and R. J. D. Miller, Nature 496, 343 (2013).