Electron Correlation Effects in Frustrated Itinerant Electron Systems

在这个项目中，我们研究了强关联电子系统中的各种有趣的现象，这些系统在自旋和轨道自由度的影响下受到几何挫折。我们还致力于全面理解凝聚态物理学的基本问题，即“电子相关性和量子涨落”。为了从理论上处理这些具有大量子涨落的系统，我们需要使用超出平均场理论的复杂方法。一般情况下，很难处理这样的问题，包括强电子关联和几何挫折。我们使用了一种强有力的方法，即所谓的动力学集团近似，它使我们能够系统地研究阻挫电子系统。此外，我们利用计算机辅助强耦合团簇展开时，我们接近的问题，从绝缘方面，而在金属区，我们已经使用变分Monte Carl ...更多信息 我们系统地研究了自旋、电荷和轨道自由度相互作用引起的有趣现象。特别是，我们集中在量子相变和相关的临界现象。这样，我们就从微观角度对强关联电子系统的动力学进行了理论研究。我们着重研究了以下六个问题：1.阻挫Mott绝缘体中的空穴效应; 2.自旋冰系统中的阻挫效应; 3.阻挫引起的自发降维; 4. Kondo效应与RKKY相互作用之间的竞争; 5.自旋自由度与轨道自由度之间的竞争和相互作用; 6. Kagome和Checker上的关联电子系统。上述结果已在几种国际期刊上发表（30篇原创论文）。此外，我们还在国际会议和研讨会上报告了成果（12次特邀演讲）。虽然研究已经进行了系统性的研究，但仍存在与实验的定量比较，这将在未来的工作中考虑。少

In this project, we have studied a variety of interesting phenomena in strongly correlated electron systems, which are subject to geometrical frustration under the influence of spin and orbital degrees of freedom. We have also aimed at comprehensive understanding of the fundamental problem of condensed matter physics, i.e. "electron correlations and quantum fluctuations". In order to theoretically treat these systems with large quantum fluctuations, we need make use of sophisticated methods beyond mean-field theory. In general, it is difficult to deal with such problems including both strong electron correlations and geometrical frustration. We have used a powerful method, the so-called dynamical cluster approximation, which enables us to study frustrated electron systems systematically. Also, we have exploited the computer-aided strong-coupling cluster expansion when we approach the problem from the insulating side, while in the metallic region, we have used the variational Monte Carl … More o method, etc. We have systematically investigated the interesting phenomena originating from the interplay of spin, charge and orbital degrees of freedom. In particular, we have focused on quantum phase transitions and related critical phenomena. In this way, we have studied the dynamics of strongly correlated electron systems theoretically from the microscopic point of view. We have investigated the above problem with particular emphasis on the following six subjects.1.hole-doing effect into frustrated Mott insulator.2.frustration effects in spin-ice systems.3.spontaneous dimensional-reduction due to frustration4.competition between the Kondo effect and the RKKY interaction.5.competition and interplay between spin and orbital degrees of freedom.6.correlated electron systems on the Kagome and checker-board lattice.The above results have been published (30 original papers) in several international journals. Also, we have reported the results (12 invited talks) in the international conferences and symposia. Although the research has been performed systematically, there still remains the quantitative comparison with experiments, which will be considered in the future work. Less