Studies on inhomogeneous electronic structures in high J_c ceramics superconductors

高J_c陶瓷超导体非均匀电子结构研究

• 批准号: 11650692
• 负责人: HASEGAWA Tetsuya
• 金额: $ 2.18万
• 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 (C)
• 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/grant/KAKENHI-PROJECT-11650692/
• 关键词: STM; tunneling spectroscopy; local density of states; high T_c superconductors; critical current density; pinning site; 臨界電流; 磁束ピニング; 走査プローブ顕微鏡; 超伝導ギャップ

In order to clarify the inhomogeneous electronic structures responsible for high critical current densities (J_c) in high T_c superconductors, we have performed scanning tunneling microscopy/spectroscopy (STM/STS) on NdBaCuO and Pb-doped BiSrCaCuO, being promising candidates for practical high J_c materials, at low temperatures below T_cIn NdBaCuO, we reproducibly found a clear. superconducting gap structure with 2Δ〜50 meV, which is in agreement with the literature data. The shape of the background conductance is fairly flat, contrary to the most of the tunneling data of the Y123 exhibiting the parabolic one. On the as-cleaved surfaces, we have frequently seen narrow spatial regions with in-gap conductance peaks, possibly originating from quasi-particle scattering by atomic scale defects, such as oxygen vacancy. These regions are thought to act as strong pinning centers.In Pb-doped BiSrCaCuO, we have succeeded in visualizing phase separation into Pb-poor and Pb-rich regions. From the STM/STS measurements around liquid nitrogen temperature, it has been revealed that the former has higher T_c than the latter. In addition, the interface between two regions are quite sharp, 〜several nm. Therefore, it is expected that the interfaces effectively trap vortices particularly at higher temperatures.

为了阐明高 T_c 超导体中高临界电流密度 (J_c) 的不均匀电子结构，我们对 NdBaCuO 和掺铅 BiSrCaCuO 进行了扫描隧道显微镜/光谱 (STM/STS)，它们是实际高 J_c 的有希望的候选者材料，在低于 T_cIn NdBaCuO 的低温下，我们重复地发现了清晰的超导间隙结构。 2Δ〜50 meV，这与文献数据一致，背景电导的形状相当平坦，与大多数在解理表面上表现出抛物线形状的隧道数据相反。看到具有间隙内电导峰值的狭窄空间区域，可能源于原子级缺陷（例如氧空位）的准粒子散射，这些区域被认为是强钉扎中心。 Pb 掺杂的 BiSrCaCuO，我们成功地将相分离可视化为贫铅区和富铅区，从液氮温度附近的 STM/STS 测量结果表明，前者的 T_c 高于后者。两个区域之间的界面非常尖锐，约几个纳米，因此，预计界面可以有效地捕获涡流，特别是在较高温度下。

项目成果

X.Zhao,T.Hasegawa ら: ""STM/STS Observations of Co Impurities in Bi2.1Sr1.8Ca(Cu1-xCox)2O8+y Single Crystals""Physica B. (in press).

X.Zhao、T.Hasekawa 等人：“Bi2.1Sr1.8Ca(Cu1-xCox)2O8+y 单晶中 Co 杂质的 STM/STS 观察”“Physica B.（出版中）。

S.Nakao,T.Hasegawa ら: ""Electronic Structures of Two-Phase Microstructures in Pb-Doped Bi2Sr2CaCu2Oy""J.Low Temp.Phys.. in press.

S.Nakao、T.Hasekawa 等人：“Pb 掺杂 Bi2Sr2CaCu2Oy 中两相微结构的电子结构””J.Low Temp.Phys.. 正在出版。

X.Zhao,S.Nakao,K.Ueno,G.Kinoda,T.Endo,T.Hasegawa et al.: "STM/STS Observations of Co Impurities in Bi2.1Sr1.8Ca (Cu1-xCox) 2O8+y Single Crystals"Physica B. 284-288. 1065-1066 (2000)

X.Zhao,S.Nakao,K.Ueno,G.Kinoda,T.Endo,T.Hasekawa 等人：“Bi2.1Sr1.8Ca (Cu1-xCox) 2O8 y 单晶中 Co 杂质的 STM/STS 观察

T.Hasegawa, M.Z.Lin and O.Shiino: ""Scanning Tunneling Spectroscopy of Layered Cuprates and Transition Metal Chalcogenides" "Spectroscopy of Layered Materials", ed. H.P.Hughes"Kluwer Publishers. 403-443 (2000)

T.Hasekawa、M.Z.Lin 和 O.Shiino：“层状铜酸盐和过渡金属硫族化物的扫描隧道光谱”“层状材料的光谱”，H.P.Hughes 编辑”Kluwer 出版社。

G.Kinoda, T.Yamanouchi, J.Kasai, T.Endo, X.Zhao, K.Kitazawa and T.Hasegawa: "Cryogenic STM/STS Observation of NdBa_2Cu_3O_<7-δ> Single Crystals"Physica B. 284-288. 971-972 (2000)

G.Kinoda、T.Yamanouchi、J.Kasai、T.Endo、X.Zhao、K.Kitazawa 和 T.Hasekawa：“NdBa_2Cu_3O_<7-δ> 单晶的低温 STM/STS 观察”Physica B. 284-288 .971-972 (2000)