Nanosecond dynamics of phase transitions in chromophoredoped ferroelectric crystals

The microscopic dynamics of phase transitions in ferroelectric crystals are studied using time-resolved fluorescence spectroscopy. Fluorescence decay times of the molecular probe tryptophan, embedded in the ferroelectric crystals potassium dihydrogen phosphate (KDP) and triglycine sulfate (TGS), are measured over a large temperature range. The dependence of the lifetime data on temperature were different between the two crystals. The magnitude of the fluorescence lifetime shows a rapid change around the phase transition temperature in KDP, while the changes in the lifetime data of the TGS crystal have been smooth. The data indicate that the order of the phase transition in solids (first or second) can be recovered using this technique. Since fluorescence lifetime is related to the dynamic interactions between the chromophore and the environment, insight into the emergence of macroscopic phase transition behavior from microscopic fluctuations near the phase transition region may be realized.