| Project/Area Number |
17340088
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 |
TAKESADA Masaki Hokkaido University, Faculty of Science, Lecturer (30311434)
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| Co-Investigator(Kenkyū-buntansha) |
ONODERA Akira Hokkaido University, Faculty of Science, Professor (40142682)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥14,520,000 (Direct Cost: ¥14,100,000、Indirect Cost: ¥420,000)
Fiscal Year 2007: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2006: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2005: ¥11,200,000 (Direct Cost: ¥11,200,000)
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| Keywords | photo induced phase transition / quantum paraelectrics / inorganic ferroelectrics / vibronic soft mode / soft mode dynamics / bismuth lavered perovskite / photoinduced quantum cooperative phenomenon / photoinduced dielectric susceptibility / ダイナミクス / 低振動数光散乱 / Ni-doped KTaO_3 / 強誘電性量子協力現象 / 光誘起協力現象 / ソフトモード完全凍結 / 量子強誘電体 / 低振動数ラマン散乱 / 光誘起バイブロニック強誘電性 / SrTi^<18>O_3 / 電子-格子相互作用 / バイブロニック強誘電性 / ソフトモード / 量子常誘電性 / 量子強誘電性 / 光誘起超低振動ラマン散乱 |
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| Research Abstract |
Phase transition and its control by external stimulation have attracted much attention because of not only for basic research but also for wide applications. In particular, sensitive response to external stimulations including light can be extended in the cooperative system close to phase transition point. However, many previous works have focused mainly on organic strongly correlated electron systems. An exploration of new system for a photoinduced phase transition is important subject for further research progress. Recently, in the quantum paraelectric perovskites, SrTiO3 and KTaO3, an anomalous increase of dielectric constant has been observed as a new photoinduced cooperative phenomenon. In the present study we investigate extremely low frequency Raman spectra under UV excitation on perovskites and bismuth-layered perovskites to clarify the dynamical property on photoinduced cooperative phenomena of the quantum paraelectrics and ferroelectrics. In this study we obtained the followi
… More
ng conclusions.
1. A perfect softening of the ferroelectric mode has been observed in the isotope-induced ferroelectric SrTi18O3 by a high-resolution technique using a Sandercock-type tandem Fabry-Perot interferometer. The mechanism of the phase transition is concluded to be an ideal displacive-type with perfect softening. From the difference between the soft mode behavior of quantum paraelectric SrTi16O3 and ferroelectric SrTi18O3, the photoinduced cooperative phenomenon observed in quantum paraelectrics should originate in a vibronic coupling between the ferroelectric soft mode and a photoinduced state.
2. An appearance of new central peak related with a photoinduced state and an anomalous instability of the soft mode behavior were observed in layered perovskite oxides by the high-resolution light scattering technique. The obtained results are the first report of the Raman scattering spectra that indicate the existence of photoinduced state. Further systematical investigation using the high resolution light scattering technique will discover a new class of a quantum ferroelectric cooperative phenomenon. Less
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