Anomolous Charge Transfer in High-Tc Superconducting Oxides Probed by Raman Scattering

拉曼散射探测高温超导氧化物中的反常电荷转移

• 批准号: 08455012
• 负责人: KAKIHANA Masato
• 金额: $ 4.74万
• 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: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08455012/
• 关键词: High-Tc superconductors; Raman scattering; Charge transfer; Metal-insulator transition; Carrier distribution; Screening effects; Phonon; Photoinduced phase transition; 高温超伝導体

The superconductivity in copper-based high-Tc superconducting oxides is intimately linked with the insulator-to-metal transitions, which are induced by carrier doping into the parent insulator. In this study, Raman scattering has been used as a tool to monitor the charge transfer and charge redistribution near the insulator-to-metal transitions induced by atomic substitutions (doping). The system chosen for the study includes Bi2Sr2Ca1-xYxCu2O8+d (x=0-1), and thier Raman spectra have been investigated in a number of well-defined single crystal and polycrystalline samples. From the polarization and Y-doping dependence ; and from a comparison with previous reports on Bi-based cuprates, we have for the first time established clearly mode assignments of the 7 modes that are Raman allowed within the ideal body-centered tetragonal unit-cell. For instance, confusions of the assignments for the two most prominent Raman bands around 630 cm-1 and 460 cm-1 have been solved without ambiguity in th … More is study by the single-crystal polarized Raman measurements including the difficult c-axis polarized geometry. A more exciting result in this study was that the direct evidence for a decreased number of hole carriers onto the CuO2 planes was extracted from the change in intensities of phonon modes associated with CuO2 plane vibrations : i.e.with increasing Y doping we find that the vibrational modes involving atoms in the CuO2 planes rapidly increase in intensity as a result of the reduced metallic screening in the hole-depleted Y doped samples. Similar intensity variations have been found in almost all the known high-Tc superconducting oxides with different hole concentration. We have proposed that the hole concentration of a given superconducting sample (thereby superconducting transition temperature Tc) can be estimated by measuring the Raman intensity of the CuO2 plane. During the course of this study, we have also discovered in oxygen depleted Y-based high-Tc superconductors unusual phase transitions at room temperature induced by visible light irradiations (photoinduced phase transition), which may open up new opportunities for future industrial applications. Less

铜基高温超导氧化物的超导性与绝缘体到金属的转变密切相关，这是由载流子掺杂到母体绝缘体中引起的。在这项研究中，拉曼散射被用作监测电荷的工具。由原子取代（掺杂）引起的绝缘体到金属转变附近的转移和电荷重新分布 选择用于研究的系统包括Bi2Sr2Ca1-xYxCu2O8+d (x=0-1) 及其拉曼光谱已在许多明确的单晶和多晶样品中进行了研究，从偏振和 Y 掺杂依赖性以及与之前的报告进行比较；基于双基铜酸盐，我们首次建立了理想体心四方晶胞内拉曼允许的 7 种模式的清晰模式分配。例如，630 cm-1 和 460 cm-1 附近两个最突出的拉曼谱带的分配混乱已经得到解决，并且在这一点上没有歧义……更多的是通过单晶偏振拉曼测量进行的研究，包括困难的 c 轴偏振几何结构这项研究中一个更令人兴奋的结果是，从与 CuO2 平面振动相关的声子模式强度的变化中提取了 CuO2 平面上空穴载流子数量减少的直接证据。 ：即随着 Y 掺杂的增加，我们发现由于空穴耗尽的 Y 掺杂样品中金属屏蔽的减少，涉及 CuO2 平面中原子的振动模式强度迅速增加，在几乎所有已知的已知样品中都发现了类似的强度变化。我们提出，可以通过测量 CuO2 的拉曼强度来估计给定超导样品的空穴浓度（从而超导转变温度 Tc）。在这项研究过程中，我们还发现贫氧钇基高温超导体在可见光照射下会发生异常的相变（光致相变），这可能为未来的工业应用开辟新的机会。 。较少的

项目成果

Kakihana,Osada,Kall,Borjesson,Mazaki,Yasuoka,Yashima,Yoshimura: "Raman active phonons in Bi_2Sr_2Co_<1-x>Y_xCu_2O_<8+d>(x=0-1)Effects of hole-filling and internal pressure induced by Y doping for Ca,and implications on Phonon assignments" Physical Review

Kakihana，Osada，Kall，Borjesson，Mazaki，Yasuoka，Yashima，Yoshimura：“Bi_2Sr_2Co_<1-x>Y_xCu_2O_<8 d>(x=0-1)中Y引起的孔填充和内部压力的拉曼活性声子

垣花 眞人: "YBa_<2-x>Sr_xCu_3O_<7-d>における酸素の無秩序化と電荷移動効果" 粉体および粉末冶金. 43.2. 195-199 (1996)

Masato Kakihana：“YBa_<2-x>Sr_xCu_3O_<7-d> 中的氧无序和电荷转移效应”粉末和粉末冶金 43.2 (1996)。

Osada,Kakihana,Kall,Borjesson,Yashima,Yoshimura: "Change in phonon Raman spectra of Bi_2Sr_2Ca_<1-x>Y_xCu_2O_<8+d> induced by hole filling and implications for phonon assignments" Materials Science and Engineering B. 41. 107-110 (1996)

Osada，Kakihana，Kall，Borjesson，Yashima，Yoshimura：“空穴填充引起的 Bi_2Sr_2Ca_<1-x>Y_xCu_2O_<8 d> 声子拉曼光谱的变化及其对声子分配的影响”材料科学与工程 B. 41. 107-

M.Kall: "Phonon Raman scattering in Y_<1-x>Pr_xBa_2Cu_4O_8(x=0-1)and (Y_<1-x>Pr_x)_2Ba_4Cu_7O_<15-d>(x=0-0.6)" Physical Review. B53.22. 3590-3597 (1996)

M.Kall：“Y_<1-x>Pr_xBa_2Cu_4O_8(x=0-1)和 (Y_<1-x>Pr_x)_2Ba_4Cu_7O_<15-d>(x=0-0.6) 中的声子拉曼散射”物理评论。

M.Osada: "Change in phnon Raman spectra of Bi_2Sr_2Ca_<1-x>Y_xCu_2O_<8+d> induced by hole filling and implications for phonon assignments" Materials Science and Engineering. B41.1. 107-110 (1996)

M.Osada：“空穴填充引起的 Bi_2Sr_2Ca_<1-x>Y_xCu_2O_<8 d> 声子拉曼光谱的变化及其对声子分配的影响”材料科学与工程。