权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Development of a unified theory for the dynamical mean-field and the spin fluctuations in strongly_correlated electron systems

强相关电子系统动态平均场和自旋涨落统一理论的发展

基本信息

批准号：
11640367
负责人：
SASO Tetsuro
金额：
$ 1.98万
依托单位：
Saitama University
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 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640367/
关键词：
strongly correlated electron systems dynamical mean field theory spin fluctuation thermoelectric power quantum dot Kondo effect magnetic impurity many-body effect 動的分子場重い電子系

项目摘要

In this project, I have developed a unified theory of the dynamical mean field (DMFT) and self-consistently renormalized spin-fluctuations (SCR) for the strongly correlated electron systems. To do this, I have formulated a new scheme of the modified perturbation theory which is used to solve the effective impurity problem in our unified theory. Then, I obtained the local and bulk dynamical susceptibility, to which I have introduced a condition similar to that in SCR to control the amplitude of the magnetic moment. The present theory exhibits the same critical behaviors in the vicinity of the quantum critical point (QCP) as SCR, but can incorporate, beyond SCR, the effects of strong correlation and the structures of specific materials at finite energy and temperature. I have applied the theory to the single-band Hubbard model and confirmed that it really works well. The modified perturbation theory for impurity is extended to the case of the orbital degeneracy. I have also applied the t … More wo-particle-self-consistent theory (TPSC) of spin fluctuations to the impurity Anderson model, and found that it does not yield the correct low energy scale in the strong correlation limit. It was shown that the improvement of this point leads to our unified theory.I have also studied the Kondo insulators, paying special attention to FeSi, which has been considered to be a typical example of the materials described by SCR. I have reinvestigated this material from the viewpoint of the strong correlation and clarified that the temperature dependence of the optical conductivity can be explained only by the many-body effect. Recently, the Kondo insulators are attracting researchers' interest because they are the candidates for a good thermoelectric device. Since the thermoelectric properties could be much affected by the spin fluctuations, we have studied FeSi and YbB_12 as important materials. I found that the thermopower of FeSi can be explained by the assumption that a small amount of holes are introduced to the simplified two-band model obtained from the band-calculation. The similar model cannot explain temperature dependence of the thermopower of YbB12. I found that the strong correlation effects are crucial to understand this material. Less

在这个项目中，我发展了强关联电子系统的动力学平均场和自洽重整化自旋涨落的统一理论。为了做到这一点，我已经制定了一个新的计划，修改的微扰理论是用来解决我们的统一理论中的有效杂质问题。然后，我得到了局部和整体的动力学磁化率，我引入了一个类似于SCR的条件来控制磁矩的幅度。本理论在量子临界点（QCP）附近表现出与SCR相同的临界行为，但可以在SCR之外纳入强相关性的影响和特定材料在有限能量和温度下的结构。我已经将该理论应用于单带Hubbard模型，并证实它确实工作得很好。将修正的杂质微扰理论推广到轨道简并的情形。我也应用了t ...更多信息将自旋涨落的双粒子自洽理论（TPSC）应用于杂质安德森模型，发现在强关联极限下不能得到正确的低能标度。结果表明，这一点的改进导致了我们的统一理论。我还研究了近藤绝缘体，特别注意FeSi，它被认为是SCR描述的材料的典型例子。我从强关联的观点重新研究了这种材料，阐明了光电导率的温度依赖性只能用多体效应来解释。近藤绝缘体是一种性能优良的热电器件，近年来引起了研究人员的极大兴趣。由于自旋涨落对热电性能的影响很大，我们将FeSi和YbB_（12）作为重要材料进行了研究。我发现，热电势的FeSi可以解释的假设，少量的空穴被引入到简化的双带模型从能带计算得到的。类似的模型不能解释YbB_（12）热电势的温度依赖性。我发现，强相关效应对于理解这种材料至关重要。少