| アブストラクト: |
The emergence of ultra-fast X-ray diffraction paves the way for direct
structural investigation of the nature of photo-induced phase
transformation. Thus, it is now possible to record complete diffraction
patterns with appropriate time resolution using the pulse structure of
synchrotron sources, giving an outstanding opportunity to directly observe
the photo-induced structural changes and symmetry breaking. In that frame,
we will present the structural evidence of the photo-induced phase
transformation in molecular charge-transfer insulating materials from a
neutral paraelectric phase to a metastable ionic one, on the 100 picosecond
time-scale. The X-ray diffraction data show that light directly triggers a
self-organized ferroelectric long-range order. This observation provides a
new way for optically coherent control of phase transition. In addition this
gives new directions in the use of ultra-fast time-resolved crystallography,
in particular with the development of femto-second X-ray sources which will
make possible the study of precursor phenomena, such as coherent phonons and
nano-domain formation.
|
