| 重电子系统中的关联效应 |
| Alternative Title | Correlation effect in heavy electron system
|
| 钟寅 |
| Thesis Advisor | 罗洪刚
|
| 2016-05-30
|
| Degree Grantor | 兰州大学
|
| Place of Conferral | 兰州
|
| Degree Name | 博士
|
| Keyword | 重费米子
拓扑近藤绝缘体
非费米液体
d 波超导
|
| Abstract | 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。 |
| Other Abstract | The heavy fermion/electron system is one of the most active and promising
research fields in modern condensed matter physics, in which countless emergent
phenomena appears like heavy Fermi liquid behavior, unconventional superconductivity, strange metal, quantum criticality and so on. However, due to the
electron correlation effect which cannot be captured by conventional mean-field
and perturbation theory, the theoretical study in this field is slow and does not
receive proper attention. But, we perceive that slave-particle-based mean-field approach and numerical techniques like quantum Monte Carlo and dynamic meanfield theory have changed this trend and it is our opportunity to immerse into
this fruitful but largely unexplored field. In this thesis, we have systematically
studied electron correlation effect in heavy fermion systems in terms of model
Hamiltonian, e.g. Kondo lattice and periodic Anderson lattice model, via both
analytical and numerical techniques. Specifically, we have provided an alternative
description of quantum criticality in terms of orbital-selective orthogonal metal
transition, which is obtained by applying novel Z2 slave-spin mean-field theory.
The divergent specific heat and quasi-linear-T resistance is reproduced and is
consistent with experiments. Next, turning on spin-orbit coupling, we have found
topological antiferromagnetic spin-density-wave on Haldane-Kondo lattice model. The unique feature of such state is the non-trivial quantum Hall response to
external electromagnetic field, which is obviously beyond the framework of topological Kondo insulator. Then, we further explore possible topological properties
in Kondo-necklace model with the help of quantum non-linear sigma model and
appropriate topological term. It is found that Kondo-necklace model in two or
three dimensions may support certain kinds of symmetry-protected topological
states. Motivated by recent experiments in CeCoIn5, we have studied fermionology and unconventional superconductivity in Kondo-Heisenberg model, which gives
rise to a unified description of normal state Fermi surface and the origin of pairing
instability. Finally, constraint path Monte Carlo method is explained in detail
and applied to periodic Anderson model, where good agreement with previous
works is shown. We hope the present work may be helpful for understanding the
complex phenomena in heavy fermion materials. |
| URL | 查看原文
|
| Language | 中文
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| Document Type | 学位论文
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| Identifier | https://ir.lzu.edu.cn/handle/262010/229008
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| Collection | 物理科学与技术学院
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Recommended Citation
GB/T 7714 |
钟寅. 重电子系统中的关联效应[D]. 兰州. 兰州大学,2016.
|
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