We use the topological heavy fermion (THF) model and its Kondo Lattice (KL) formulation to study the symmetric Kondo state in twisted bilayer graphene. Via a large-N approximation, we find a symmetric Kondo (SK) state in KL mode at fillings $ν=0,\pm 1,\pm 2$. In the SK state, all symmetries are preserved and the local moments are Kondo screened by the conduction electrons. At the mean-field level of the THF model at $ν=0,\pm 1, \pm 2, \pm 3$, we also find a similar symmetric state. We study the stability of the symmetric state by comparing its energy with the ordered states and find the ordered states to have lower energy. However, moving away from integer fillings by doping holes to the light bands, we find the energy difference is reduced, which suggests the loss of ordering and a tendency towards Kondo screening. In order to include many-body effects beyond the mean-field approximation, we perform dynamical mean-field theory (DMFT) calculations on the THF model. We find the spin susceptibility follows a Curie behavior at $ν=0, \pm 1,\pm 2$ down to $\sim 2\text{K}$ where the onset of screening of the local moment becomes visible. This hints to very low Kondo temperatures at these fillings, in agreement with the outcome of our mean-field calculations. At non-integer filling $ν=\pm 0.5,\pm 0.8,\pm 1.2$ DMFT shows deviations from a $1/T$-susceptibility at much higher temperatures, suggesting a more effective screening of local moments with doping. Finally, we study the effect of a $C_{3z}$-rotational-symmetry-breaking strain via mean-field approaches and find that a symmetric phase (that only breaks $C_{3z}$ symmetry) can be stabilized at sufficiently large strain at $ν=0,\pm 1, \pm 2$. Our results suggest that a symmetric Kondo phase is strongly suppressed at integer fillings, but could be stabilized either at non-integer fillings or by applying strain.
Electronic structure and magnetic correlations in the epitaxially strained bilayer nickelate La$_3$Ni$_2$O$_{7}$
M. N. Mikheev Institute of Metal Physics, Russian Academy of Sciences（俄罗斯科学院 M.N. 米凯耶夫金属物理研究所）；Institute of Physics and Technology, Ural Federal University（乌拉尔联邦大学物理与技术学院）
Emergence of a symmetry-broken Chern insulator near a moiré Kondo breakdown
Shanghai Jiao Tong University（上海交通大学）；Cornell University（康奈尔大学）；Kavli Institute at Cornell for Nanoscale Science（康奈尔纳米科学卡弗里研究所）；Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学李政道研究所）；National Institute for Materials Science（国立材料研究所）；Hefei National Laboratory（合肥国家实验室）；Max Planck Institute for the Structure and Dynamics of Matter（马克斯·普朗克物质结构动力学研究所）
Mott-Derived Local Moments and Kondo Hybridization in a d-electron Kagome lattice
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；University of Chinese Academy of Sciences（中国科学院大学）；State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University（清华大学物理系低维量子物理国家重点实验室）；National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University（南京大学固体微结构物理全国重点实验室及物理学院）；Technical Institute of Physics and Chemistry, Chinese Academy of Sciences（中国科学院化学物理研究所）
Distinguishing Mott and strain-induced anisotropic semimetals in magic-angle twisted bilayer graphene using Landau level spectroscopy
National High Magnetic Field Laboratory（国家强磁场实验室）；Florida State University（佛罗里达州立大学）；Princeton University（普林斯顿大学）；Weizmann Institute of Science（魏茨曼科学研究所）；University of California Santa Barbara（加州大学圣塔芭芭拉分校）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）；IKERBASQUE, Basque Foundation for Science（伊克尔巴斯基克，巴斯克科学基金会）；University of Minnesota（明尼苏达大学）
IMDEA Nanoscience（IMDEA纳米科学研究所）；Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University（武汉大学物理科学与技术学院人工微纳结构教育部重点实验室）；School of Artificial Intelligence, Wuhan University（武汉大学人工智能学院）；Wuhan Institute of Quantum Technology（武汉量子技术研究院）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）
