Dresden 2014 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 46: Low-Dimensional Systems: Molecular Conductors
TT 46.7: Talk
Tuesday, April 1, 2014, 15:30–15:45, HSZ 204
Photo-induced phase transition in TTF-CA — •Patricia Haremski, Tobias Peterseim, Tomislav Ivek, and Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart, Germany
30 years ago, the first experiments on photo-induced phase transitions on the quasi 1D organic mixed-stacked TTF-CA salt paved the way for numerous experimental and theoretical studies on nonequilibrium states. TTF-CA shows a neutral (N) to ionic (I) phase transition at TNI = 81.5 K with a change of ionicity from 0.2 (N) to 0.6 (I) and a dimerization of TTF and CA molecules along the stacking direction. Step-Scan FTIR spectroscopy was used to investigate the photo-induced transitions in TTF-CA by pulsed laser excitation. For different temperatures below TNI and different laser intensities, temporal changes of the infrared reflection spectrum with polarization parallel and perpendicular to the stacking direction were recorded. The reduction of the ag-modes intensity indicates that the dimerization is dissolved and metastable domains are created. The temporal evolution of the changes in reflectivity can be described by a non-exponential decay function and exhibits similarities to the decay process observed in 1D random-walk annihilation process in photo-excited polyacetylen. Due to the multi-instability in the vicinity of TNI, large domains are formed with an extended lifetime in the microsecond range.