近藤格点系统中的自旋轨道耦合和拓扑量子态

Spin-orbit coupling has attracted intensive interests in understading the formation of macroscopic quantum phases emergent from 5d-compounds or correlated electron materials, but the physical effects driven by the spin-orbit coupling coming from itinerant electrons in 4f-electron-contained compounds is a till an unexplored new topic. Recent experiments have discovered complicated yet robust surface states in the Kondo insulating SmB6 compound. The observation strongly indicate that a topological non-trivial Kondo screened singlet state, as well as other novel spin-orbit-coupling-related quantum states, could be stabilized in reality in heavy fermion compounds. In this Project, we will investigate, in a systematical manner, the formation and evolution of such Kondo state, and the corresponding electronic structure and topological property in a class of 5d-4f systems. Our studies will be framed on the microscopic many-electron model Hamiltonians and effective quantum field theories and renormalization group methods will be ultilized. We will distinct two kinds of spin-orbit couplings: the one is due to the 5d electrons, another is due to the 4f electrons. We will focus on the evolution of the Kondo screened singled state with varying RKKY interaction or frustrations, and the resulting competing magnetic or superconducting ordered states due to symmetry breakings. Our special attentions will be paied to the interply between spin-orbit coupling and Kondo effect, and their influences on the formations of novel quantum phases as well as topological orders. We will also clarify several intriguing basic theoretical issues related to Kondo screening or Kondo entanglement. We expect that our theoretical studies can not only explain the relevant observations in heavy fermion compounds but also motivate new experiments along this direction.

由相对论效应导致的自旋轨道耦合对重元素（如5d电子）及关联电子体系中宏观量子态的影响正在引起人们的关注，而巡游电子自旋轨道耦合在4f电子化合物中产生的物理效应则是一个全新课题。最近实验上观测到近藤绝缘体SmB6中复杂的表面态，预示重费米子化合物可能出现与自旋轨道耦合有关的拓扑非平凡近藤屏蔽单态以及其它有趣的奇特量子态。本项目拟从多电子微观模型出发，以有效量子场论和重整化群方法为主要手段，系统性地研究5d-4f近藤格点体系中自旋轨道耦合对近藤效应和电子结构拓扑性质的影响。我们将考察源于5d电子和4f电子不同自旋轨道耦合所带来的区别，重点研究近藤屏蔽态随RKKY相互作用或量子阻挫的演化规律，探索该体系中对称性破缺导致磁性或超导态的形成机理。这些研究有望揭示关联电子体系中自旋轨道耦合对奇特量子态和拓扑序形成的具体作用，澄清与近藤屏蔽相联系的一些理论问题,解释或预言相关实验中的重要物理现象。

本项目《近藤格点系统中的自旋轨道耦合和拓扑量子态》以自旋轨道耦合和电子关联效应引起的宏观量子态为目标，研究以f－电子系统为代表的、也包括其它d－电子系统或巡游电子系统中可能出现与自旋轨道耦合有关的拓扑非平凡量子态。在项目实施过程中我们基本按照这些目标执行了主要研究内容，其中理论研究从多电子微观模型出发，结合材料的第一性原理计算，同时我们注重和实验研究紧密结合，重点对自旋轨道耦合、近藤屏蔽效应、电子结构拓扑性质等问题开展研究，并试图理解这些体系中呈现的一些奇特量子输运行为， 如超导、半金属性、巨磁阻、量子震荡等等。其中的一些问题是在原定计划的基础上，根据这一领域最新发展而提出并加以研究的。其中的一些研究揭示关联电子体系中自旋轨道耦合对奇特量子态和拓扑序形成的具体作用，解释或预言相关实验中的重要物理现象。