Theoretical study on magnetism and superconductivity in almost lo-calized strongly correlated elecron systems

近局域强关联电子系统磁性和超导性的理论研究

• 批准号: 08640434
• 负责人: OHKAWA Fusayoshi
• 金额: $ 1.47万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640434/
• 关键词: Kondo effect; local quantum spin fluctuations; 1; d expansion; local-moment magnetism; itinerant-electron magnetism; high-temperature superconducticity; Curie-Weiss law; metamagnetism; 強相関電子系; 磁性; 超伝導; スピン揺動; 強相関電子

One of the most important issues for magnetism is to construct a unified theory that is applicable to both local-moment magnetism and itinerant electron magnetism. The 1/d expansion methof has been developed, with d being the spatial dimensionality. This is apllicable to both local-moment magnetism and itinerant electron magnetism. Local quantuam spin fluctuations can be correctly considered in the best single-site approximation (SSA). The SSA is equivalent to solving a mapped Anderson model to be self-consistently determined form a maaping condition. This means that the Kondo effect plays a significant and essential role in not only dilute magnetic alloys but also periodical strongly correlated electron systems. Intersite effects can be perturbatively treated starting from the SSA.Various issues have been studied by the 1/d expansion method. (1) The corssover of magnetic structures between sinusoidal and helical stuructures has been studied. (2) There is another mechanism of the Curie-Weiss law for itinerant electron magnetism besides the mode-mode coupling mechanism, which is of higher in 1/d : the temperature dependence of the magnetic mean field, which is of leading order in l/d. (3) A mechanism of high-temperature superconductivity in cuprate-oxide superconductors has been proposed ; the formation of dx_<x2-y2> wave Cooper pairs between heavy quasiparticles in the vicinity, of the Mott transtion. The main pairing interaction is the superexchange interaction between nearest neighbors. (4) A new type of magnetic exchange interaction has been studied. It is caused by the virtual exchange of pair excitatiolns of quasiparticles in spin channels, has been studied. The strength of this exchange interaction is about the bandwidth of quisipartgicles. (5) It has been proposed that a metamagnetic transition in CeRu_2Si_2 is mainly caused by this exchange interaction.

磁性的最重要问题之一是构建一种适用于局部命令和巡回电子磁性的统一理论。已经开发了1/D扩展的Methof，D是空间维度。这对于局部时刻磁力和巡回电子磁性都是可相当的。可以在最佳的单位点近似（SSA）中正确考虑局部Quantuam自旋波动。 SSA等同于求解映射的安德森模型，以形成自以为是的，形成了一种障碍条件。这意味着近藤效应在不仅稀释的磁合金，而且在周期性密切相关的电子系统中起着重要而重要的作用。从SSA开始，可以通过1/d扩展方法研究了各种问题。 （1）已经研究了正弦和螺旋结构之间的磁性结构的紧身室。 （2）除了模式模式耦合机制外，还有库里 - 韦斯定律的另一种机制，用于巡回电子磁性，这在1/d中较高：磁平均场的温度依赖性，这是L/d中的领先顺序。 （3）已经提出了一种高温超导性超导性的机制； dx_ <x2-y2>在附近，莫特·特兰斯翁（Mott Transtion）附近的重准颗粒之间的波库珀对形成。主要的配对相互作用是最近邻居之间的互相交互。 （4）已经研究了一种新型的磁交换相互作用。已经研究了这是由旋转通道中准粒子的一对兴奋性的虚拟交换引起的。这种交换相互作用的强度是关于Quisipartgicles的带宽。 （5）已经提出，CERU_2SI_2中的元磁过渡主要是由这种交换相互作用引起的。

项目成果

H.Satoh and F.J.Ohkawa: "Field-induced ferromagnetic exchange interactions in meta-magnetic transitions of heavy-electron liquids" Physical Review B. 57, No.3. 5891-5899 (1998)

H.Satoh 和 F.J.Ohkawa：“重电子液体元磁转变中的场感应铁磁交换相互作用”《物理评论》B. 57，第 3 期。

大川房義: "Magnetic Exchange Interactions between Quasiparticles in Itienrant-Electron Mgnets" Journal of Physical Society of Japan. 67巻2号. 525-534 (1998)

Fusayoshi Okawa：“电子磁体中准粒子之间的磁交换相互作用”，日本物理学会杂志，第 67 卷，第 2 期，525-534（1998 年）。

大川房義: "Quantum and thermal spin fluctuations in itinerant-electron magrets" Physical Review B. 57巻1号. 412-415 (1998)

Fusayoshi Okawa：“流动电子磁体中的量子和热自旋涨落”《物理评论 B》第 57 卷，第 1 期 412-415 (1998)

佐藤寛之: "Field-induced ferromagnetic Exchange Interactious in metamagnetic transitions of heavy-electron liquids" Physical Review B. 57巻3号. (1998)

Hiroyuki Sato：“重电子液体变磁转变中的场感应铁磁交换相互作用”《物理评论 B》第 57 卷，第 3 期（1998 年）

F.J.Ohkawa: "Quantum and thermal spin fluctuations in itinerant-electron magnets" Physical Review B. 57, No.1. 412-425 (1998)

F.J.Ohkawa：“流动电子磁体中的量子和热自旋波动”《物理评论》B. 57，第 1 期。