Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, P.K. 644, 48080 Bilbao, Spain.
Phys Rev Lett. 2014 May 16;112(19):197601. doi: 10.1103/PhysRevLett.112.197601. Epub 2014 May 12.
Polarized Raman, IR, and time-domain THz spectroscopy of orthorhombic lead zirconate single crystals have yielded a comprehensive picture of temperature-dependent quasiharmonic frequencies of its low-frequency phonon modes. It is argued that these modes primarily involve vibrations of Pb ions and librations of oxygen octahedra. Their relation to phonon modes of the parent cubic phase is proposed. Counts of the observed IR and Raman active modes belonging to distinct irreducible representations agree quite well with group-theory predictions. Analysis of the results yields insight into the phase transition mechanism, involving a soft ferroelectric branch coupled by a trilinear term to another two oxygen octahedra tilt modes.
正交锆酸铅单晶体的偏振拉曼、红外和时域太赫兹光谱学提供了其低频声子模式的准谐频率随温度变化的综合图像。这些模式主要涉及 Pb 离子的振动和氧八面体的摆动，这一观点得到了支持。还提出了它们与母体立方相的声子模式的关系。属于不同不可约表示的观察到的红外和拉曼活性模式的计数与群论预测非常吻合。对结果的分析深入了解了涉及通过三次项与另外两个氧八面体倾斜模式耦合的软铁电分支的相变机制。
