FEMTOSECOND TIME-RESOLVED SPECTROSCOPY OF POLARIZATION DYNAMICS IN KNBO3
FEMTOSECOND TIME-RESOLVED SPECTROSCOPY OF POLARIZATION DYNAMICS IN KNBO3
复制标题
DOI：
10.1080/00150199108216803
复制
发表时间：
1991-01-01
期刊：
影响因子：
0.8
通讯作者：
NELSON, KA
中科院分区：
文献类型：
--
作者：
DOUGHERTY, TP;WIEDERRECHT, GP;NELSON, KA
飞秒时间分辨脉冲受激散射实验进行了KNbO 3在温度跨越正交相。研究了与跃迁位移特性相关的重阻尼软光学声子模和与有序-无序特性相关的弛豫模。以前的频域光散射实验产生了相互矛盾的结果，软模式的动力学和有序无序运动的对称性。我们发现弛豫运动具有A1对称性，而软模是唯一具有B2对称性的低频激发。软模式是很好地描述了阻尼极化激元模型没有任何耦合到弛豫模式。这些结果与先前提出的八位相变模型是一致的。
Femtosecond time-resolved impulsive stimulated scattering experiments were conducted on KNbO3 at temperatures spanning the orthorhombic phase. A heavily damped soft optic phonon mode associated with the displacive character of the transition and relaxational modes associated with order-disorder character were examined. Previous frequency-domain light scattering experiments had yielded conflicting results for the dynamics of the soft mode and the symmetry of the order-disorder motions. We find the relaxational motion to be of A1 symmetry and the soft mode to be the only low-frequency exictation of B2 symmetry. The soft mode is well described by a damped polariton model without any coupling to a relaxational mode. These results are consistent with a previously proposed eight-site model for the phase transitions.