ESTABLISHMENT OF COHERENT PHONON EXCITATION --as a new method for phase transition study--

相干声子激发的建立——作为相变研究的新方法——

• 批准号: 10044050
• 负责人: YAGI Toshirou
• 金额: $ 3.71万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10044050/
• 关键词: femtosecond pulses; picosecond pulses; laser; phonon; phase transition; phonon excitation; ISRS; ISBS; 可干渉性フォノン励起; 位相マスク; ヘテロダイン検波; 超短パルスレーザー; ゆらぎ; ダイナミクス

A new experimental method COHERENT PHONON EXCITATION, which is quite adequate for the study of phase transition has been established during the period of the present research project for two years from 1998 to 2000. This method provides a direct observation of the soft excitations closely related to the phase transition dynamics. The time dependence of the motion of the soft phonon mode and/or a relaxational mode are precisely distinguishable by their time dependence because the equation of motion of thoes excitation is usually driven in the time domain. As a result of the present project, a special improvement of the experimental system has been completed using an optical interference plate (phase mask) and heterodyne detection for the light diffracted from the excited phonons. The project is summarized as follows; 1. The soft ferroelectric BィイD22ィエD2 mode of KDP has been excited and observed its time dependence as a function of temperature in a range from RT to Tc. A clear single exponential time dependence of the BィイD22ィエD2 mode even 30 K far above Tc indicates an order-disorder type phase transition dynamics in KDP. 2. A precise observation of the dispersion relation of the phonon-polariton of the ferroelectric LiNbOィイD23ィエD2 has been done at room temperature. Because the present method has advantage in a small wave vector region, the dispersion relation of the AィイD21ィエD2 phonon-polariton is determined with high accuracy elucidating a very simple curve in contrast to the several resonance points below 7THz reported in the previous studies. 3. An ultra-slow relaxational motion in the glass-liquid transition has been studied with wave vectors defined precisely.

在1998 ~ 2000年两年的研究期间，我们建立了一种新的实验方法--相干声子激发法，该方法对于相变的研究是十分合适的。这种方法提供了一个直接观察的软激发密切相关的相变动力学。软声子模式和/或弛豫模式的运动的时间依赖性可通过它们的时间依赖性精确区分，因为这些激发的运动方程通常在时域中驱动。作为本项目的结果，一个特殊的改进的实验系统已经完成，使用光学干涉板（相位掩模）和外差检测从激发声子衍射的光。本项目主要内容如下：1. KDP的软铁电B铁电D_（22）模被激发，并观察到它在RT ~ Tc范围内随温度的变化。B超晶格D22超晶格D2模在高于Tc的30 K时仍具有明显的单指数时间依赖性，表明KDP的相变动力学为有序-无序型. 2.在室温下，对LiNbO铁电体D_23-D_2的声子-极化激元色散关系进行了精确的观测。由于本方法在小波矢区具有优势，因此，与以往研究中报道的在7THz以下的几个共振点相比，本方法得到了一条非常简单的色散曲线，并得到了高精度的色散关系。3.本文用精确定义的波矢研究了玻璃-液体转变中的超慢弛豫运动。

项目成果

S.Yoshioka: "A single exponential time decay of the ferrodectric mode..."Solid State Commun.. 106・9. 577-580 (1998)

S. Yoshioka：“铁电模型的单一指数时间衰减......”Solid State Commun.. 106・9（1998）。

S.Yoshioka: "The B_2 Polariton Mode in KDP Studied by Impulsive Stimula・・・"Journal of the Physical Society of Japan. 67・7. 2178-2181 (1998)

S. Yoshioka：“脉冲刺激研究的 KDP 中的 B_2 极化子模式......”日本物理学会杂志 67・7 2178-2181（1998）。

S.Yoshioka: "The B_2 Polavifon Mode in KDP Studied by Impulsive Stimusla..."Journal of the Physical Society of Japan. 67・7. 2178-2181 (1998)

S. Yoshioka：“脉冲刺激研究的 KDP 中的 B_2 Polavifon 模式......”日本物理学会杂志 67・7 2178-2181（1998）。

Y. Tsujimi: "Anisotropic themal relaxation dynamics in TGS ・・・"Journal of the Physical Society of Japan. 67・5. 1509-1512 (1998)

Y. Tsujimi：“TGS 中的各向异性热弛豫动力学……”日本物理学会杂志 67・5（1998 年）。

S. Yoshioka, Y. Tsujimi and T. Yagi: "High frequency dielectric constant of KDP determined by polariton dispersion relation"Physica B. 263-264. 829 (1999)

S. Yoshioka、Y. Tsujimi 和 T. Yagi：“由极化子色散关系确定的 KDP 高频介电常数”Physica B. 263-264。