固有铁电体中Lifshitz点附近的声行为
Sound behavior near the Lifshitz point in proper ferroelectrics
摘要：
利用布里渊散射和超声脉冲回波技术研究了Sn 2 P2（Se0.28S0.72）6单轴铁电体的软光声子相互作用.横向声学声子和纵向和横向超声波的超声波传播方向附近的调制波矢量（在无公度相位在x>xLP）的弹性软化的超声波速度被发现在冷却到Lifshitz点的顺电相。还观察到超声衰减的强烈增加。这种现象与相对短程超声波区域中的软光学和声学分支的线性相互作用以及超声频率范围中强烈发展的长程序参数波动有关。超声波速度的温度依赖性内的Landau-Khalatnikov近似的铁电相。
英文摘要：
The interaction between soft optic and acoustic phonons was investigated for Sn2P2(Se0.28S0.72)6 proper uniaxial ferroelectrics by Brillouin scattering and ultrasonic pulse-echo techniques. The elastic softening of hypersound velocity of transverse acoustic phonons and for both longitudinal and transverse ultrasound waves which propagate near direction of the modulation wave vector (in the incommensurate phase at x>xLP) was found at cooling to the Lifshitz point in the paraelectric phase. The strong increase of the ultrasound attenuation have also been observed. Such phenomena are related to the linear interaction of the soft optic and acoustic branches in the region of relatively short-range hypersound waves and to the strongly developed long-range order parameter fluctuations in the ultrasound frequency range. The hypersound velocity temperature dependence was described within the Landau-Khalatnikov approximation for the ferroelectric phase.
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