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A study on cooperation and competition between the magnetic correlation and transport properties in systems with localized and itinerant electrons

局域电子和巡回电子体系中磁相关性与输运性质的合作与竞争研究

基本信息

批准号：
10304026
负责人：
YAMADA Kazuyoshi
金额：
$ 20.49万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2001
项目状态：
已结题

项目摘要

In this program, we systematically studied cooperation or competition between magnetic order or fluctuation and superconductivity of strongly correlated electron systems such as high temperature superconductors and uranium compounds by using neutron scattering and other microscopic techniques on single crystals with high quality.The superconductivity in the high temperature cuprates appears by carrier doping into the Mott insulators. In recent years, the self-organization of the doped carriers was found in these cuprates particularly in the 2-1-4 type cuprates. One of the main issues is whether the self-organization commonly occurs in other types of cuprates and induces novel quantum properties such as high temperature superconductivity. Although this issue is still continuing, in this program we could provide several key experimental results for the elucidation of this problem.In the study on the uranium compounds particularly on UPd_2Al_3 , we completed a model for the paring mechanism, where three 5f-electrons of U play a role differently for the superconductivity in this compound ; one constructs a magnetic framework and the other forms the Cooper paring through the magnetic excitations of the framework. It turns out this model can explain not only the symmetry of the superconductivity also many of the physical properties of this system.As seen in UPd_2Al_3 the possibility of contribution from different types of electrons for mechanism of the paring force in the high temperature superconductor will be one of the main issues and elucidated if one succeeds in distinguishing the intrinsic electronic inhomogeneity from that caused by the chemical randomness by doping carriers.

在本项目中，我们利用中子散射等显微技术，在高质量单晶上系统地研究了高温超导体和铀化合物等强关联电子系统中磁有序或涨落与超导电性之间的协同或竞争，高温铜氧化物中的超导电性是通过载流子掺杂到Mott绝缘体中而出现的。近年来，在这些铜氧化物中发现了掺杂载流子的自组织现象，特别是在2-1-4型铜氧化物中。其中一个主要的问题是，自组织是否普遍发生在其他类型的铜酸盐，并诱导新的量子特性，如高温超导。虽然这一问题仍在继续，但在本项目中我们可以提供几个关键的实验结果来阐明这一问题：在对铀化合物特别是UPd_2Al_3的研究中，我们完成了一个配对机制的模型，其中U的三个5 f电子对该化合物的超导电性起不同的作用;一种是构建磁性骨架，另一种是通过骨架的磁激发形成库珀配对。结果表明，该模型不仅可以解释超导性的对称性，而且可以解释该系统的许多物理性质。3.高温超导体中不同类型的电子对配对力机制的贡献的可能性将是主要问题之一，如果人们成功地区分出本征电子不均匀性和化学物质引起的不均匀性，通过掺杂载流子的随机性。