Universal understanding of pressure-induced quantum paraelectric state
| Project/Area Number |
17540287
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics I
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| Research Institution | Hokkaido University |
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Principal Investigator |
TSUJIMI Yuhji Hokkaido University, Research Institute for Electronic Science, Associate Professor, 電子科学研究所, 助教授 (20113673)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | Quantum paraelectrics / Strontium titanate / Light scatterin / Broad doublet / Ferroelectric regions / Length scale / 誘電体物性 |
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| Research Abstract |
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.
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Report
(3 results)
Research Products
(13 results)
