| Project/Area Number |
17540307
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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 | High energy accelerator research organization |
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Principal Investigator |
NASU Keiichiro High energy accelerator research organization, Institute of materials structure science, Professor, 物質構造科学研究所, 教授 (90114595)
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| Co-Investigator(Kenkyū-buntansha) |
富田 憲一 大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 助手 (70290848)
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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 |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2005: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | SrTiO_3 / soft-anharmonic phonon / charged ferroelectric domain / bipolaron clusters / KTaO_3 / 非平衡相転移 / ソフト・フォノン / 3次元ペロブスカイト / KTaO3 / シミュレーション / 3次元ペロブスカイ / 光誘起相転移 / 数値シュミレーション / SrTiO3 |
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| Research Abstract |
In connection with the recent experimental discoveries on photo-enhancements of the electronic conductivity and the quasi-static electric susceptibility in SrTiO_3, we theoretically study a photogeneration mechanism of charged ferroelectric domains in this perovskite type quantum dielectric. The photogenerated electron, being quite itinerant in the 3d band of Ti^<4+>, is assumed to couple weakly but quadratically with soft-anharmonic T_<1u> phonons in this quantum dielectric. This photogenerated electron is also assumed to couple strongly but linearly with the breathing (A_<1g>) type high energy phonons. Using a discrete model, we will show that these two types of electron-phonon couplings result in two types of polarons, a "super-para-electric large polaron" with a quasi-global parity violation, and an "off center type self-trapped polaron" with only a local parity violation. We will also show that this super-para-electric large polaron is nothing else but a singly charged (e^-) and conductive ferroelectric domain with a quasi macroscopic size. This large polaron is also shown to aggregate with other same polarons, resulting in large bipolarons and their clusters.
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