Precompression engineering of metal-insulator transition and magnetism in designed breathing kagome systems
School of Physics and Astronomy, and Key Laboratory of Multiscale Spin Physics (Ministry of Education), Beijing Normal University（北京师范大学物理与天文学院，多尺度自旋物理教育部重点实验室）；College of Physics, Hebei Normal University, and Hebei Advanced Thin Films Laboratory（河北师范大学物理学院，河北省先进薄膜实验室）
Qingzhuo Duan, Hongdao Zhuge, Ying Liang, Tianxing Ma
Kagome materials featuring dispersive Dirac cones and topological flat bands exhibit unique electronic and magnetic properties. However, kagome compounds with tunable electrical conductivity remain scarce, which severely impedes their device applications. Here, based on density functional theory (DFT) and Boltzmann transport theory, we introduce the breathing effect into kagome materials $\mathrm{Nb_3XCl_7}$ (X = F, Cl, Br, I) via chemical precompression, thereby inducing a metal-insulator transition and magnetic variation. We determine that the band structures, optical absorption spectra and magnetic ground states agree well with experimental results at the effective correlation strength $U_{\text{eff}} = 2$ eV. The calculated conductivity and magnetic properties reveal that the monolayer $\mathrm{Nb_3Cl_8}$ and $\mathrm{Nb_3XCl_7}$ undergoes transitions from paramagnetic metals to Mott insulators at $U_{\text{eff}} = 1$ eV and $t_{\text{out}}/t_{\text{in}} = 0.6674$, respectively. Our detailed analysis establishes that the stronger breathing effect corresponds to enhanced chemical precompression, which reduces the region of free electron gas between intercell Nb atoms and facilitates the metal-insulator transition. Finally, we propose several viable synthesis routes for $\mathrm{Nb_3FCl_7}$, $\mathrm{Nb_3BrCl_7}$, and $\mathrm{Nb_3ICl_7}$, providing predictive guidance for experimental studies. Our study establishes a practical framework for investigating the breathing effect in correlated kagome systems and yields valuable insights into the mechanisms underlying metal-insulator transition and magnetic properties in real breathing kagome materials.
Tunable quantum spin liquidity in the 1/6th-filled breathing kagome lattice
我们提出了一系列材料，Li $_2$ In $_{1-x}$ Sc $_x$ Mo $_3$ O $_8$，可以被描述为1/6填充呼吸戈薇晶格的测量。用Sc代替In产生化学压力，其非单调地改变呼吸参数。$μ$ SR实验表明，该化学压力将系统从反铁长程序调谐到量子自旋液体相。与呼吸参数的强相关性意味着它是控制磁挫挫水平的主导参数，增加的kagome对称性产生量子自旋液体相。磁化率测量表明，这与晶格对称性变化引起的不同类型的电荷有序有关，符合Chen等人的理论[Phys. Rev. B 93，245134（2016）]。在中等Sc浓度和最小呼吸参数下，样品的比热与预测的$U(1)$量子自旋液体一致。
High-pressure modulation of breathing kagome lattice: Cascade of Lifshitz transitions and evolution of the electronic structure
Helmholtz-Zentrum Dresden-Rossendorf（德累斯顿罗森多夫赫尔姆霍兹中心）；TUD Dresden University of Technology（德累斯顿工业大学）；Universität Stuttgart（斯图加特大学）；Synchrotron SOLEIL（索雷尔同步辐射中心）；ESRF（欧洲同步辐射装置）；ShanghaiTech University（上海科技大学）；Renmin University of China（中国人民大学）
Emergent orbitals in the cluster Mott insulator on a breathing Kagome lattice
基于团簇Mott绝缘材料LiZn $_2$ Mo $_3$ O $_8$的最新进展，我们考虑了呼吸Kagome晶格上扩展哈伯德模型的强元胞电荷有序区，揭示了团簇Mottness的性质.格点电荷序是由格点间电荷相互作用和六边形格点上三个局域电子的集体运动引起的。该模型自然导致局部矩减少2/3，如在LiZn $_2$ Mo $_3$ O $_8$中所观察到的。此外，在低温下，每个六边形元格除了剩余的1/2自旋外，还包含额外的类轨道自由度。我们探讨的后果，这紧急轨道自由度。我们指出，局域矩之间的相互作用是自然描述的Kugel-Khomskii自旋轨道模型。我们发展了一个部分子方法，并提出了一个自旋液体基态与自旋费米表面的模型。我们进一步预测了当系统处于强磁场下时，系统会出现一个新的轨道序。讨论了LiZn $_2$ Mo $_3$ O $_8$的各种实验结果，包括一个论点，即如果每个Mo的电荷稍微偏离化学计量，则电荷排序会很短。
Theory of Ca$_{10}$Cr$_7$O$_{28}$ as a bilayer breathing-kagome magnet: Classical thermodynamics and semi-classical dynamics
Ca $_{10}$ Cr $_7$ O $_{28}$是一种新型的自旋- $1/2$磁体，其表现出自旋液体行为，这使其有别于任何先前研究的模型或材料。然而，理解Ca $_{10}$ Cr $_7$ O $_{28}$提出了一个重大挑战，因为晶体结构的低对称性导致非常复杂的相互作用，在晶胞中具有多达七个不等价的耦合参数。在这里，我们探索的起源自旋液体行为的钙$_{10}$铬$_7$ O $_{28}$，从最简单的微观模型与实验一致-海森堡模型的呼吸kagome（BBK）晶格的单双层。我们使用经典的Monte Carlo（MC）模拟和（半）经典的分子动力学（MD）模拟相结合来探索该模型的热力学和动力学性质，并将这些与Ca $_{10}$ Cr $_7$ O $_{28}$的实验结果进行比较.我们揭示了在不同时间尺度上的性质不同的行为，并认为Ca $_{10}$ Cr $_7$ O $_{28}$的基态是从缓慢波动的“螺旋自旋液体”中产生的，而更快的波动则反映了在可果梅反铁磁体中发现的U（1）自旋液体。我们还确定了纵向和横向自旋激发在外加磁场的关键区别，并认为这些是一个显着的特点，在BBK模型的自旋液体。
Magnetic Anisotropies and Skyrmion Lattice Related to Magnetic Quadrupole Interactions of the RKKY Mechanism in Frustrated Spin-Trimer System Gd$_{3}$Ru$_{4}$Al$_{12}$ with a Breathing Kagome Structure
Anomalous Hall Response Induced by Correlated Disorder in the Breathing Kagome Lattice Mn$_{3}$Sn
Oak Ridge National Laboratory（橡树岭国家实验室）；The Pennsylvania State University（宾夕法尼亚州立大学）；Weizmann Institute of Science（魏茨曼科学研究所）；Brigham Young University（杨百翰大学）；Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所）；Brookhaven National Laboratory（布鲁克海文国家实验室）
From strong to weak correlations in breathing-mode kagome van der Waals materials: Nb$_3$(F,Cl,Br,I)$_8$ as a robust and versatile platform for many-body engineering
Radboud University（拉德堡德大学）；University of Groningen（格罗宁根大学）；Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam（阿姆斯特丹大学物理学院范德瓦尔斯-泽曼研究所）；Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University（奥胡斯大学跨学科纳米科学中心（iNANO）物理与天文学系）
