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As is well-known, the ferroelectric modes play an important roll\u003cbr /\u003ein the dielectric property, transportation and phase transition or these materials.\u003cbr /\u003eMany efforts were already performed on the connection of this ferroelectric mode\u003cbr /\u003ewith the quartic or sextic anharmonic oscillators. ln experiment, glgantic\u003cbr /\u003ephoto-enhancements of the electronic conductivity and the dielectric constant have\u003cbr /\u003erecently been observed in SrTiO3. lt was also pointed out that, this dielectric\u003cbr /\u003eenhancement remains to exist only under the ultraviolet (UV) illumination, while\u003cbr /\u003evanishes as the illumination is turned off. As for the photo-induced electronic\u003cbr /\u003econduction in SrTiO\u003csub\u003e3\u003c/sub\u003e, it is expected to be an alternative mechanism from that of the\u003cbr /\u003eordinary field induced one in metallic systems. However, the microscopic origin of\u003cbr /\u003ethese photo-induced phenomena has not yet been clarified theoretically. Thus, this\u003cbr /\u003eis just the motivation of the present study.\u003cbr /\u003e We will give a short introduction to the soft mode theory in the\u003cbr /\u003esecond chapter since our work will be mainly based on this theory.\u003cbr /\u003eThe spatial structure and the electronic property of this 3D\u003cbr /\u003eperovskite. SrTi0\u003csub\u003e3\u003c/sub\u003e, are also stated. since we will focus our efforts\u003cbr /\u003eonly on this compound in the present work. Some key points of the\u003cbr /\u003eprevious studies on the fundamental properties of SrTiO\u003csub\u003e3\u003c/sub\u003e, are\u003cbr /\u003esummerized as well. =n Chapter 3, a detailed illustration is given\u003cbr /\u003eto the Super-Para-Electric (SPE) large polarons, from the set-up of\u003cbr /\u003ethe cheoretic model to the numerical calculatlons, and ends up with\u003cbr /\u003ethe impurity effect on this polaron. Combining the experimentally\u003cbr /\u003eobserved dielectrlc and conductive properties with previous\u003cbr /\u003etheoretical researches on the model for this crystal, we give a further\u003cbr /\u003einvestigation into the model and come up with a new model for the\u003cbr /\u003ephoto excited state of the crystal. By which, we can adiabatically\u003cbr /\u003eobtain the corresponding energy surface and find all the metastable\u003cbr /\u003estates on it. With the investigation of each of such states, We can\u003cbr /\u003efind its connection with the dielectric and conductive property of\u003cbr /\u003ethis crystal・ We also give an investigation into the most stable\u003cbr /\u003equasiparticle state for the many electron system within the adeabatic\u003cbr /\u003emethod and give a description to the possible lattice configurations\u003cbr /\u003efor the photo excited state of the electron and phonon coupling system.\u003cbr /\u003eThen it is followed by Chapter 4, the appllcations of this SPE polaron\u003cbr /\u003etheory in the interpretation of the photo-induced giant dielectric\u003cbr /\u003econstant and electronic conductivity. We will first discuss one of\u003cbr /\u003ethe fundamental problems for phonons, phonon softening or phonon\u003cbr /\u003ehardening with the introduction of e-p coupling. Then we will apply\u003cbr /\u003eour SPE large polaron theory to the experimentally observed static\u003cbr /\u003edielectric enhancement in srTiO\u003csub\u003e3\u003c/sub\u003e, clarifying the microscopic origin \u003cbr /\u003eof this photo-induced phase transition. In the following, we will\u003cbr /\u003egive a phenomenological interpretation to the experimentally reported\u003cbr /\u003emetallic conduction in SrTiO\u003csub\u003e3\u003c/sub\u003e by studying the translational property\u003cbr /\u003eof the polarons. In Chapter 5, we will discuss the relaxation process\u003cbr /\u003eof the lattice after the photo-excitation. It has already been studied\u003cbr /\u003ethat for polymers, the formation of the polaron or exciton is an\u003cbr /\u003eultra-fast process. \u003csup\u003e[6l]\u003c/sup\u003e In experiment, these states could be detected\u003cbr /\u003eand predicted from the spectra. However, by virtue of the molecular\u003cbr /\u003edynamics theory, the information of the lattice configuration as well\u003cbr /\u003eas the electronic state can be traced so as to compare with the\u003cbr /\u003eenergetic evolution. Then, the lattice relaxation process could be\u003cbr /\u003erecognized more clearly. We will first give a deschption to the \u003cbr /\u003emolecular dynamics theory for the e-p interacting system. Then, we\u003cbr /\u003ewill apply this method to SrTiO\u003csub\u003e3\u003c/sub\u003e and give some detailed descriptions\u003cbr /\u003eabout the relaxation process in this crystal. We will show the\u003cbr /\u003eformation of the SPE large polaron is an ultra-fast process of about\u003cbr /\u003eseveral picoseconds, and how the electron and phonon interaction\u003cbr /\u003esystem releases its energy so as to reach its new stable state. The\u003cbr /\u003einfluence of the electron and phonon interaction strength and the\u003cbr /\u003esize of the electron and phonon coupling system on the relaxation\u003cbr /\u003eprocess will be shown. A summary of all the conclusions of these\u003cbr /\u003estudies is given at Chapter 6.", "subitem_description_type": "Other"}]}, "item_1_description_7": {"attribute_name": "学位記番号", "attribute_value_mlt": [{"subitem_description": "総研大甲第989号", "subitem_description_type": "Other"}]}, "item_1_select_14": {"attribute_name": "所蔵", "attribute_value_mlt": [{"subitem_select_item": "有"}]}, "item_1_select_8": {"attribute_name": "研究科", "attribute_value_mlt": [{"subitem_select_item": "高エネルギー加速器科学研究科"}]}, "item_1_select_9": {"attribute_name": "専攻", "attribute_value_mlt": [{"subitem_select_item": "13 物質構造科学専攻"}]}, "item_1_text_10": {"attribute_name": "学位授与年度", "attribute_value_mlt": [{"subitem_text_value": "2006"}]}, "item_creator": {"attribute_name": "著者", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "QIU, Yu", "creatorNameLang": "en"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_files": {"attribute_name": "ファイル情報", "attribute_type": "file", "attribute_value_mlt": [{"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 0, "filename": "甲989_要旨.pdf", "filesize": [{"value": "265.9 kB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 265900.0, "url": {"label": "要旨・審査要旨", "url": "https://ir.soken.ac.jp/record/674/files/甲989_要旨.pdf"}, "version_id": "4542bfbc-ae83-4a24-b6a8-58f50a69a08f"}, {"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 1, "filename": "甲989_本文.pdf", "filesize": [{"value": "4.9 MB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 4900000.0, "url": {"label": "本文", "url": "https://ir.soken.ac.jp/record/674/files/甲989_本文.pdf"}, "version_id": "936fb837-dafc-4109-b8b8-33a704a4ca80"}]}, "item_language": {"attribute_name": "言語", "attribute_value_mlt": [{"subitem_language": "eng"}]}, "item_resource_type": {"attribute_name": "資源タイプ", "attribute_value_mlt": [{"resourcetype": "thesis", "resourceuri": "http://purl.org/coar/resource_type/c_46ec"}]}, "item_title": "Dual Electron-phonon Coupling Model for Giant Photoenhancements of Dielectric Constant and Electronic Conductivity in SrTiO3", "item_titles": {"attribute_name": "タイトル", "attribute_value_mlt": [{"subitem_title": "Dual Electron-phonon Coupling Model for Giant Photoenhancements of Dielectric Constant and Electronic Conductivity in SrTiO3"}, {"subitem_title": "Dual Electron-phonon Coupling Model for Giant Photoenhancements of Dielectric Constant and Electronic Conductivity in SrTiO3", "subitem_title_language": "en"}]}, "item_type_id": "1", "owner": "1", "path": ["15"], "permalink_uri": "https://ir.soken.ac.jp/records/674", "pubdate": {"attribute_name": "公開日", "attribute_value": "2010-02-22"}, "publish_date": "2010-02-22", "publish_status": "0", "recid": "674", "relation": {}, "relation_version_is_last": true, "title": ["Dual Electron-phonon Coupling Model for Giant Photoenhancements of Dielectric Constant and Electronic Conductivity in SrTiO3"], "weko_shared_id": 1}
Dual Electron-phonon Coupling Model for Giant Photoenhancements of Dielectric Constant and Electronic Conductivity in SrTiO3
https://ir.soken.ac.jp/records/674
https://ir.soken.ac.jp/records/674dc97c1de-530f-44c9-8655-fdb938456caf
名前 / ファイル | ライセンス | アクション |
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Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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公開日 | 2010-02-22 | |||||
タイトル | ||||||
タイトル | Dual Electron-phonon Coupling Model for Giant Photoenhancements of Dielectric Constant and Electronic Conductivity in SrTiO3 | |||||
タイトル | ||||||
言語 | en | |||||
タイトル | Dual Electron-phonon Coupling Model for Giant Photoenhancements of Dielectric Constant and Electronic Conductivity in SrTiO3 | |||||
言語 | ||||||
言語 | eng | |||||
資源タイプ | ||||||
資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
資源タイプ | thesis | |||||
著者名 |
邱, 宇
× 邱, 宇 |
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フリガナ |
クイユ
× クイユ |
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著者 |
QIU, Yu
× QIU, Yu |
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学位授与機関 | ||||||
学位授与機関名 | 総合研究大学院大学 | |||||
学位名 | ||||||
学位名 | 博士(理学) | |||||
学位記番号 | ||||||
内容記述タイプ | Other | |||||
内容記述 | 総研大甲第989号 | |||||
研究科 | ||||||
値 | 高エネルギー加速器科学研究科 | |||||
専攻 | ||||||
値 | 13 物質構造科学専攻 | |||||
学位授与年月日 | ||||||
学位授与年月日 | 2006-09-29 | |||||
学位授与年度 | ||||||
2006 | ||||||
要旨 | ||||||
内容記述タイプ | Other | |||||
内容記述 | Since some 3D type perovkite compounds have been found in the experiments to<br />give gigantic dielectric constant, in contrast to the ordinary dielectrics, its<br />underlying microscopic mechanism has attractted much attention in the field of<br />solid state theory. As is well-known, the ferroelectric modes play an important roll<br />in the dielectric property, transportation and phase transition or these materials.<br />Many efforts were already performed on the connection of this ferroelectric mode<br />with the quartic or sextic anharmonic oscillators. ln experiment, glgantic<br />photo-enhancements of the electronic conductivity and the dielectric constant have<br />recently been observed in SrTiO3. lt was also pointed out that, this dielectric<br />enhancement remains to exist only under the ultraviolet (UV) illumination, while<br />vanishes as the illumination is turned off. As for the photo-induced electronic<br />conduction in SrTiO<sub>3</sub>, it is expected to be an alternative mechanism from that of the<br />ordinary field induced one in metallic systems. However, the microscopic origin of<br />these photo-induced phenomena has not yet been clarified theoretically. Thus, this<br />is just the motivation of the present study.<br /> We will give a short introduction to the soft mode theory in the<br />second chapter since our work will be mainly based on this theory.<br />The spatial structure and the electronic property of this 3D<br />perovskite. SrTi0<sub>3</sub>, are also stated. since we will focus our efforts<br />only on this compound in the present work. Some key points of the<br />previous studies on the fundamental properties of SrTiO<sub>3</sub>, are<br />summerized as well. =n Chapter 3, a detailed illustration is given<br />to the Super-Para-Electric (SPE) large polarons, from the set-up of<br />the cheoretic model to the numerical calculatlons, and ends up with<br />the impurity effect on this polaron. Combining the experimentally<br />observed dielectrlc and conductive properties with previous<br />theoretical researches on the model for this crystal, we give a further<br />investigation into the model and come up with a new model for the<br />photo excited state of the crystal. By which, we can adiabatically<br />obtain the corresponding energy surface and find all the metastable<br />states on it. With the investigation of each of such states, We can<br />find its connection with the dielectric and conductive property of<br />this crystal・ We also give an investigation into the most stable<br />quasiparticle state for the many electron system within the adeabatic<br />method and give a description to the possible lattice configurations<br />for the photo excited state of the electron and phonon coupling system.<br />Then it is followed by Chapter 4, the appllcations of this SPE polaron<br />theory in the interpretation of the photo-induced giant dielectric<br />constant and electronic conductivity. We will first discuss one of<br />the fundamental problems for phonons, phonon softening or phonon<br />hardening with the introduction of e-p coupling. Then we will apply<br />our SPE large polaron theory to the experimentally observed static<br />dielectric enhancement in srTiO<sub>3</sub>, clarifying the microscopic origin <br />of this photo-induced phase transition. In the following, we will<br />give a phenomenological interpretation to the experimentally reported<br />metallic conduction in SrTiO<sub>3</sub> by studying the translational property<br />of the polarons. In Chapter 5, we will discuss the relaxation process<br />of the lattice after the photo-excitation. It has already been studied<br />that for polymers, the formation of the polaron or exciton is an<br />ultra-fast process. <sup>[6l]</sup> In experiment, these states could be detected<br />and predicted from the spectra. However, by virtue of the molecular<br />dynamics theory, the information of the lattice configuration as well<br />as the electronic state can be traced so as to compare with the<br />energetic evolution. Then, the lattice relaxation process could be<br />recognized more clearly. We will first give a deschption to the <br />molecular dynamics theory for the e-p interacting system. Then, we<br />will apply this method to SrTiO<sub>3</sub> and give some detailed descriptions<br />about the relaxation process in this crystal. We will show the<br />formation of the SPE large polaron is an ultra-fast process of about<br />several picoseconds, and how the electron and phonon interaction<br />system releases its energy so as to reach its new stable state. The<br />influence of the electron and phonon interaction strength and the<br />size of the electron and phonon coupling system on the relaxation<br />process will be shown. A summary of all the conclusions of these<br />studies is given at Chapter 6. | |||||
所蔵 | ||||||
値 | 有 |