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Condensed Molecular Materials (CM2) Seminar

Lecture Title "Structural dynamics of photoinduced molecular switching in the solid state"
Date Friday 21 August 2009 14:00
Lecturer Prof. Hervé Cailleau (Institut de Physique de Rennes, Université de Rennes 1)
Place

201 Seminar Room, Main Office Building of IMS
Summary

A current challenge in science and technology is to direct the functionality of matter at the relevant smaller scale, not only ultra-small size but also ultra-short time. Thus a femtosecond laser pulse may induce spectacular collective and/or cooperative phenomena in the solid state. This can trigger the transformation of the material towards another macroscopic state of different electronic and/or structural order, for instance from non magnetic to magnetic or from insulator to conductor. Besides different itinerant electron systems materials with multi-functional molecules which can switch between two states are also promising. The switching of molecules in a material triggered by a femtosecond light pulse ensues the now established field of femtochemistry in solution where photo-chemical processes are essentially independent. The physical picture of the dynamics of this switching in molecular materials will be discussed. The key point is that in the solid state different degrees of freedom of different nature play their part on different time scales and the pathway is complex, from the molecular to material length and time scales. The discussion will be based on recent investigation of the structural dynamics in multifunctional spin crossover compounds which are prototypes of molecular bistability in the solid state. The time-resolved x-ray diffraction and optical results show the dynamics span from subpicosecond molecular photoswitching followed by volume expansion (nanosecond) and thermal switching (microsecond).
Contact

Kenji Yonemitsu, kxy@ims.ac.jp
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