Search for oxides showing reversible changes in structure upon visible light illumination by Raman scattering and ellucidation of its mechanism

通过拉曼散射寻找可见光照射下结构可逆变化的氧化物并阐明其机制

• 批准号: 11450246
• 负责人: KAKIHANA Masato
• 金额: $ 7.42万
• 依托单位: TOKYO INSTITUTE OF TECHNOLOGY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450246/
• 关键词: Raman Scattering; Oxide; Visible light; light-induced structural change; oxide superconductor; Visible-light structure change; charge transfer; 可逆的構造変化

The aim of this study is to develop a convenient means toward the discovery of oxides showing changes in their structure under light illumination. In order to choose a new candidate from a numerous number of oxides, one has to monitor precisely a subtle change in structure induced by light illumination. To explore an oxide showing structural change under a specific visible light and to ellucidate its mechanism, the in-situ Raman scattering experiment, which enabled us to observe the change in structure, has been carried out using a variety of lasers (Kr, dye, Ti sapphire etc.) as an excitation source for the Raman spectra. We were able to evaluate the magnitude of interaction between the substance and light, making possible to choose the candidate oxide showing the light-induced structural change. It was the slightly oxygen-deficient YBa_2Cu_3O_x (hereinafter, referred to Y123) that was discovered in this way.In order to know the mechanism for the light-induced structural change in Y123 systems, it was ellucidated (1) at what part the phenomenon takes place in the crystal structure and (2) which electronic transition is essential to the phenomenon. Since a given vibrational mode associated with a specific atom could be each individually observed by polarized Raman scattering, the place at which the light-induced structural change occurs has been specified. As a result, the active site was ellucidated to be within the one dimensional CuO chain. The minimum energy triggering the phenomenon was determined to be 2.15 eV by a series of Raman scattering experiments using light sources with wave lengths ranging from 363 to 800 nm, and it has turned out that the origin of the electronic transition corresponds to a charge transfer of a molecular-like Cu-O.

本研究的目的是开发一种便捷的方法来发现在光照射下结构发生变化的氧化物。为了从众多氧化物中选择一种新的候选物，人们必须精确监测光照射引起的结构的微妙变化。为了探索在特定可见光下表现出结构变化的氧化物并阐明其机制，我们使用各种激光（Kr、染料、钛蓝宝石等）作为拉曼光谱的激发源。我们能够评估物质与光之间相互作用的程度，从而可以选择显示光诱导结构变化的候选氧化物。这样发现的就是微缺氧的YBa_2Cu_3O_x（以下简称Y123）。为了了解Y123体系中光致结构变化的机理，阐明了（1）在什么部位发生了这种现象发生在晶体结构中，并且 (2) 哪种电子跃迁对该现象至关重要。由于与特定原子相关的给定振动模式可以通过偏振拉曼散射单独观察到，因此光引起的结构变化发生的位置已经被指定。结果表明，活性位点位于一维 CuO 链内。通过使用波长范围为 363 至 800 nm 的光源进行的一系列拉曼散射实验，确定触发该现象的最小能量为 2.15 eV，并且证明电子跃迁的起源对应于分子状的Cu-O。

项目成果

M.Osada, M.Kakihana: "Photoinduced Metastability in YBa_2Cu_3O_x studied by insitu Raman scattering"Physica B. 284-288. 681-682 (2000)

M.Osada、M.Kakihana：“通过原位拉曼散射研究 YBa_2Cu_3O_x 中的光诱导亚稳定性”Physica B. 284-288。

M.Kakihana: "Raman active modes in Nd_2BaCu_3O_z compound"Physica C. 338. 151-156 (2000)

M.Kakihana：“Nd_2BaCu_3O_z 化合物中的拉曼活性模式”Physica C. 338. 151-156 (2000)

M.Kakihana: "Raman active modes in Nd_2BaCu_3O_2 compound"Physica C. 338. 151-156 (2000)

M.Kakihana：“Nd_2BaCu_3O_2 化合物中的拉曼活性模式”Physica C. 338. 151-156 (2000)

M.Kakihana, M.Osada: "Raman spectroscopy as a unique tool for characterizing high-Tc superconducting oxides"Physica C. 338. 144-150 (2000)

M.Kakihana、M.Osada：“拉曼光谱作为表征高温超导氧化物的独特工具”Physica C. 338. 144-150 (2000)

M.Kakihan,M.Osada: "Raman scattering in YBa_2Cu_4O_8 and PrBa_2Cu_4O_8 : Indications of pseudogap effects in nonsuperconducting PrBa_2Cu_4O_8"Physical Review B. 61. 7049-7054 (2000)

M.Kakihan,M.Osada：“YBa_2Cu_4O_8 和 PrBa_2Cu_4O_8 中的拉曼散射：非超导 PrBa_2Cu_4O_8 中赝能隙效应的指示”物理评论 B.61.7049-7054 (2000)