利用场论分析和密度矩阵重整化群（DMRG）方法，研究了一维强关联量子系统实现拓扑有序的Half相位基态的理论模型.该模型由自旋为1/2的海森堡链通过两种不同类型的竞争近藤交换耦合耦合到紧束缚链组成：“s波”近藤耦合（$J^s_{K}$）和不太常见的“p波”（$J^p_{K}$）近藤耦合。虽然第一种耦合是在许多凝聚态系统中研究的标准Kondo相互作用，但后者最近已由Alexandrov和Coleman [Phys. Rev. B 90，115147（2014）]引入，作为导致一维拓扑Kondo绝缘基态的可能机制。作为这种竞争的结果，拓扑量子相变（TQPT）发生在系统中的比率$J^s_{K}/J^p_{K}$的临界值，分离（Haldane型）拓扑相位从拓扑平凡的基态，其中该系统可以基本上被描述为本地单态的产品。我们从基态的磁化强度分布、纠缠熵和全纠缠谱等方面研究了TQPT。我们的研究结果可能是相关的理解如何拓扑有序阶段的费米子出现在强相互作用的量子系统。
英文摘要：
We investigate, by means of a field-theory analysis combined with the density-matrix renormalization group (DMRG) method, a theoretical model for a strongly correlated quantum system in one dimension realizing a topologically-ordered Haldane phase ground state. The model consists of a spin-1/2 Heisenberg chain coupled to a tight-binding chain via two competing Kondo exchange couplings of different type: a "s-wave" Kondo coupling ($J^s_{K}$), and a less common "p-wave" ($J^p_{K}$) Kondo coupling. While the first coupling is the standard Kondo interaction studied in many condensed-matter systems, the latter has been recently introduced by Alexandrov and Coleman [Phys. Rev. B 90, 115147 (2014)] as a possible mechanism leading to a topological Kondo-insulating ground state in one dimension. As a result of this competition, a topological quantum phase transition (TQPT) occurs in the system for a critical value of the ratio $J^s_{K}/J^p_{K}$, separating a (Haldane-type) topological phase from a topologically trivial ground state where the system can be essentially described as a product of local singlets. We study and characterize the TQPT by means for the magnetization profile, the entanglement entropy and the full entanglement spectrum of the ground state. Our results might be relevant to understand how topologically-ordered phases of fermions emerge in strongly interacting quantum systems.
Kondo insulators are strongly correlated system in which a clean insulating gap emerges only at very low temperature due to many-body effects involving localized $f$-electrons. However, certain Kondo insulators, like SmB$_6$ and Ce${_3}$Bi${_4}$Pt${_3}$, display metallic behaviors at extremely low temperatures, that have defied current understanding. Recent advances in topological effects in materials has raised the attention on the protected surface states in these "topological Kondo insulators" as a potential resolution to some of the puzzling behaviors. Here we resolve these puzzles via a d…
Impurities and defects in Kondo insulators can have an unusual impact on dynamics that blends with effects of intrinsic electron correlations. Such crystal imperfections are difficult to avoid, and their consequences are incompletely understood. Here we study magnetic impurities in Kondo insulators via perturbation theory of the s-d Kondo impurity model adapted to small bandgap insulators. The calculated magnetization and specific heat agree with recent thermodynamic measurements in samarium hexaboride (SmB$_6$). This qualitative agreement supports the physical picture of multi-channel Kondo s…
Anisotropic optical conductivity of the putative Kondo insulator CeRu$_4$Sn$_6$
近藤绝缘体，特别是它们的非立方代表仍然知之甚少。在这里，我们报告的发展各向异性的能量赝能隙的四金属化合物CeRu $_4$ Sn $_6$采用光学反射率测量在宽的频率和温度范围内，和局域密度近似加上动态平均场论计算。计算提供的证据近藤绝缘体样的响应内的$a-a$平面和更多的金属沿c轴的响应和定性再现的实验观察，帮助确定其来源。
Temperature-induced gap formation in dynamic correlation functions of the one-dimensional Kondo insulator --- Finite-temperature density-matrix renormalization-group study ---
Temperature dependent band structure of the Kondo insulator
我们提出了一个Qantum Monte Carlo（QMC）研究的近藤绝缘体的温度相关的动力学。在所谓的对称点工作允许执行无负号QMC模拟，从而达到小于传导电子带宽的1%的温度。单粒子格林函数和动态自旋关联函数的温度依赖性的研究显示了一个令人惊讶的复杂的低温能带结构，并给出了两个特征温度的证据，我们确定与近藤和相干温度，分别。特别地，数据显示在相干温度下温度诱导的金属-绝缘体转变。
The half-filled Kondo lattice model is studied at low temperatures on simple cubic lattice using the self-consistent theory developed in Phys. Rev. B 96, 075115 (2017). It is found to have three distinct insulating phases in the temperature-hopping plane, namely, the strong coupling Kondo singlet (KS) phase, the inverted Kondo singlet (iKS) phase distinguished from the KS by inversion, and the antiferromagnetic (AFM) phase. The quasiparticle density of states across the inversion transition is noted to exhibit dimensional reduction, which can differentiate between the KS and iKS insulators in …
A Mean-Field Study of Quantum Oscillations in Two-Dimensional Kondo Insulators
Max Planck Institute for the Structure and Dynamics of Matter（马克斯·普朗克物质与结构动力学研究所）；Department of Physics, University of Cincinnati（辛辛那提大学物理系）；Department of Physics and Engineering Physics, Tulane University（杜兰大学物理与工程物理系）
我们报告磁量子振荡测量使用转矩磁化近藤绝缘体Yb $_{12}$和讨论潜在的费米面的起源。观察到的量子振荡以及补充量，如有限的线性比热容在Yb $_{12}$表现出与近藤绝缘体Sm B $_6$的相似之处，但也至关重要的差异。在Yb B $_{12}$中观察到小的重费米截面，与邻近的重费米子半金属费米表面相似，而在Sm B $_6$中观察到大的轻费米表面截面，与传导电子费米表面更相似。一个丰富的频谱的理论模型，建议解释起源跨越不同的近藤绝缘家庭的散装费米表面可能从新的巡回准粒子耦合到磁场，但不耦合到弱直流电场。
A Kondo lattice is often electrically insulating at low temperatures. However, several recent experiments have detected signatures of bulk metallicity within this Kondo insulating phase. Here we visualize the real-space charge landscape within a Kondo lattice with atomic resolution using a scanning tunneling microscope. We discover nanometer-scale puddles of metallic conduction electrons centered around uranium-site substitutions in the heavy-fermion compound URu$_2$Si$_2$, and around samarium-site defects in the topological Kondo insulator SmB$_6$. These defects disturb the Kondo screening cl…
It follows from our analysis of CeRhSb that the formation of Kondo insulator state due to the presence of the collective spin singlet state is strongly reduced by its doping with various dopants when their amount exceeds 8--10\%, regardless of whether they are substituted for Ce, Rh or Sb. A wide variety of experimental results (electrical resistivity $ρ$, magnetic susceptibility $χ$, specific heat $C$, x-ray photoelectron spectroscopy) and theoretical investigations have convincingly demonstrated the proposed earlier scaling law $χ\timesρ=const.$ in the Kondo insulator regime, which is univer…
