2007 Fiscal Year Final Research Report Summary
Photoinduced Vibronic Soft mode Dynamics in Ferroelectric Quantum Cooperative Phenomena
| 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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| 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 |
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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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Research Products
(95 results)
