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Time-resolved diffraction as a tool for the study of materials science

Seminar by Professor Shin-ya Koshihara, Department of Materials Science, Tokyo Institute of Technology, Japan Photon Factory, KEK, Japan.

Abstract
Finding a system which shows phase transition triggered by external stimulation of light is becoming an attractive target for materials science. Because this class of material is a key for the basic study of non-equilibrium dynamics in condensed systems but also for achieving ultrafast photonic switching devices. Our study has focused on experimental evidences indicating that the photo-injected local excitation can really trigger the macroscopic phase transition by virtue of cooperative interactions such as spin-lattice interaction and electron-lattice coupling. This unique photo-effect has been named as photo-induced phase transition (PIPT).Combination of ultrafast lasers and synchrotron radiation sources enables time-resolved X-ray diffraction method which is revealed as a powerful tool for the PIPT research. We have constructed an in-vacuum undulator beam line NW14A as a dedicated time-resolved beam line at Photon Factory Advanced Ring (PF-AR), the High Energy Accelerator Research Organization (KEK) and started full operation from October 2006. The introduction of this new beam line will be made based on the first trial for observing time-resolved diffuse scattering to reveal the ultrafast precursor phenomena of PIPT in TTF-CA. In addition, this class of facility for dynamical structural analysis is expected to play a key role for the study of functional biological systems and chemical reactions. Related works in NW14A will be also introduced in this seminar.