重电子系统中的关联效应

发布时间：2017-12-31 07:16

  本文关键词：重电子系统中的关联效应　出处：《兰州大学》2016年博士论文　论文类型：学位论文

  更多相关文章： 重费米子 拓扑近藤绝缘体 非费米液体 d波超导

【摘要】：重费米子/电子系统是现代凝聚态物理研究中最活跃的领域之一,在这类体系中不断涌现出各类新奇的层展现象,例如重费米液体行为,非常规超导电性,奇异金属以及量子临界性。但是由于传统的平均场和微扰理论近似并不足以抓住该类系统中起主导作用的电子关联效应的本质,相关的理论研究进展相对比较缓慢且没有受到应有的重视。然而,我们发现辅助粒子基于的平均场方法和以量子蒙特卡洛与动力学平均场为代表的数值技术的发展已经改变了重费米子理论研究的原始状况,因而,在这些令人欣喜的进展鼓舞之下,我们在这篇博士论文以常见的量子晶格模型如Kondo晶格以及周期性Anderson模型出发,通过解析与数值计算方法系统化地研究重费米子体系中的电子关联效应。具体而言,我们提出了重费米子量子临界行为的一种新的理论解释,即轨道选择正交金属相变。这种基于Z2辅助自旋表示的辅助粒子形式能够正确解释实验观测到的热容对数发散以及电阻的准线性行为。当考虑自旋-轨道耦合效应时,六角近藤晶格模型可存在新有序态,即拓扑自旋密度波态。这类具有非平凡电磁响应的反铁磁自旋密度波是超越传统拓扑近藤绝缘体的新物态。为了进一步理解近藤体系的拓扑性质,我们对近藤项链模型的拓扑性质进行了探索。在这类模型中,体系的拓扑性质可由量子非线性sigma模型以及相应的拓扑项共同描述。值得注意的是,高维近藤项链模型可能支持对称保护拓扑态。最后,以Kondo-Heisenberg模型为例,研究了重费米子超导体的费米面结构以及超导配对问题。详细的计算表明局域磁性交换相互作用可诱导d波配对,超导态的物理可观测量与实验测量定性一致。这说明重费米子超导电性的某些基本性质可通过简单的BCS平均场理论得以解释。我们希望这里的研究对于进一步理解复杂的重费米物理有所裨益。
[Abstract]:Heavy fermion / electronic system is one of the most active fields in modern condensed matter physics. Various novel layering phenomena have been emerging in this kind of system, such as heavy fermion liquid behavior and unconventional superconductivity. Singular metals and quantum criticality, but because of the traditional mean field and perturbation theory approximation is not enough to grasp the essence of the electronic correlation effect which plays a leading role in this kind of systems. The relative theoretical research progress is relatively slow and has not received due attention. We find that the development of the mean field method based on the auxiliary particle and the numerical technique represented by the quantum Monte Carlo and the dynamical mean field has changed the original state of the heavy fermion theory. Encouraged by these encouraging developments, we set out in this doctoral thesis with common quantum lattice models such as Kondo lattices and periodic Anderson models. The electron correlation effect in the heavy fermion system is systematically studied by analytical and numerical methods. In particular, a new theoretical explanation of the quantum critical behavior of the heavy fermion is proposed. This auxiliary particle form based on Z2-assisted spin representation can correctly explain the logarithmic divergence of heat capacity observed in the experiment and the linear behavior of the resistor. When the spin-orbit coupling is considered, the phase transition of the orthorhombic metal is selected. Effect time. A new ordered state can be found in the lattice model of hexagonal Kondo. This kind of antiferromagnetic spin density wave with nontrivial electromagnetic response is a new physical state beyond the traditional topological Kondo insulator. In order to further understand the topological properties of Kondo system. We explore the topological properties of Kondo necklaces model, in which the topological properties of the system can be described by the quantum nonlinear sigma model and the corresponding topological terms. High-dimensional Kondo necklaces model may support symmetric protection topology. Finally, take the Kondo-Heisenberg model as an example. The Fermi surface structure and superconducting pairing of heavy fermion superconductors are studied. The detailed calculation shows that local magnetic exchange interaction can induce d wave pairing. The physical observable measurements of superconducting states are qualitatively consistent with the experimental measurements. This shows that some basic properties of the superconductivity of fermions can be explained by simple BCS mean field theory. It helps to understand complex Fermi physics.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O469
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本文编号：1358713