Universal understanding of pressure-induced quantum paraelectric state

对压力引起的量子顺电态的普遍理解

基本信息

批准号：
17540287
负责人：
TSUJIMI Yuhji
金额：
$ 2.37万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

A light scattering experiment has been performed in order to investigate precisely the dynamical nature of "quantum paraelectric phase" appearing below T=40 K in SrTi^<16>O_3 (STO16). In this phase, an unusual spectral peak called "broad doublet" (BD:〜20 GHz) emerges in the frequency region lower than the frequency of the transverse acoustic mode of lowest frequency. The purpose of present study is to clarify the physical origin of the BD.1.We have proposed that there exists a length scale (〜50 nm at T=27 K) characterizing the quantum paraelectric phase. This proposal is based on the mean free path calculation for the BD.2.SrTi^<18>O_3 (STO18: ^<16>O of SrTi^<16>O is substituted by ^<18>O) has a state such as ferroelectric phase below Tc〜29 K. We found that the spectrum of a partially softened transverse acoustic mode (STA) observed in STO18 was quite similar to that of the BD observed in STO16 at T〜20 K. We built up a hypothesis from this similarity that the physical origin of the BD emerging in STO16 is the STA. We assumed here that the dynamical ferroelectric regions (FERs: 〜50 nm at T=27 K), in which STA can propagate, exist in the quantum paraelectric phase, though matrix of STO16 is not ferroelectric but paraelectric.3.Furthermore, we found a new light scattering peak (NP:〜140 GHz) in a Nb^<5+> doped STO16. The mean free path of the NP also implies the existence of a length scale in quantum paraelectric phase. The length scale of BD and that of NP show the same temperature dependence and the same anisotropic nature. We can conclude that the unique length scale exists in the quantum paraelectric phase and that the scale characterizes the size of anisotropic FER.As known from above, the basic information on quantum paraelectric phase is not enough yet. Thus, we still continue the light scattering experiment under the atmospheric pressure to obtain that information.

为了精确研究SRTI^<16> O_3（STO16）中T = 40 K以下的“量子副层相”的动态性质，已经进行了光散射实验。在此阶段，在频率区域中出现了一个称为“宽双线”（BD：〜20 GHz）的异常光谱峰，低于最低频率的横向声模式的频率。本研究的目的是阐明BD.1.我们提出的表征量子旁拜阶段的长度尺度（〜50 nm）。该建议基于BD.2.srti ^<18> o_3（sto18： ^<16> o的平均自由路径计算，srti ^<16> o被 ^<18> o代替），其状态如tc〜29 k以下的铁电相。 Sto16中BD出现的物理起源的这种相似之处是STA。我们在这里假设动态的铁电区（fers：〜50 nm在t = 27 K时〜50 nm），其中sta可以在量子旁系阶段存在，尽管sto16的矩阵不是铁电矩阵，而是paraelectric.3.furthermore.3.furthermore，我们发现了一个新的光散射峰（np：〜140 ghz）。 NP的平均自由路径也意味着在量子降落相中存在长度尺度。 BD的长度尺度和NP的长度表现出相同的温度依赖性和相同的各向异性性质。我们可以包括唯一的长度量表存在于量子降压阶段，并且该量表以各向异性范围的大小为特征。从上方已知，量子降压阶段的基本信息还不够。这，我们仍然在大气压力下继续进行光散射实验，以获取该信息。