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

基于铜的高-TC超导氧化物中的超导性与绝缘体到金属过渡密切相关，这是通过载体掺杂到母体绝缘子引起的。在这项研究中，拉曼散射已被用作一种工具，以监测由原子取代（掺杂）引起的绝缘体到金属转变附近的电荷转移和电荷重新分布。该系统选择该研究包括BI2SR2CA1-XYXCU2O8+D（X = 0-1），并且已经在许多定义明确的单晶和多晶样品中研究了Thier Raman光谱。来自极化和浓度依赖性；从与以前关于BI基层次的报告的比较，我们首次建立了在理想的以身体为中心的四方单位电池中允许的拉曼的7个模式的明确模式分配。例如，在630 cm-1和460 cm-1左右的两个最突出的拉曼带的分配困惑已经解决了，没有歧义性……通过单晶极化拉曼测量结果进行了研究，包括困难的C轴偏光几何。 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样品。在几乎所有已知的高-TC超导氧化物具有不同孔浓度的氧化物中都发现了相似的强度变化。我们提出，可以通过测量CUO2平面的拉曼强度来估算给定超导样品的孔浓度（从而超导过渡温度TC）。在这项研究过程中，我们还发现了氧气耗尽的基于Y的高-TC超导体在室温下通过可见光照射（光诱导的相变）引起的不寻常的相变，这可能为未来的工业应用打开新的机会。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。