菱方石墨烯超晶格中近藤效应的观测
Observation of Kondo Effect in Rhombohedral Graphene Superlattices
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中文总结 AI 辅助
本研究通过磁输运与温度依赖测量，在六层菱方石墨烯莫尔超晶格中实验证实近藤效应，并揭示其可调性与近藤绝缘态的出现。
中文摘要 AI 辅助
强关联系统中的近藤效应源于巡游传导电子与局域磁矩之间的反铁磁耦合，从而产生各种奇异的量子现象。二维莫尔超晶格系统提供了一个高度可调的拓扑平带平台，其中万尼尔轨道被周期性莫尔势空间限制，并充当局域磁矩，使得近藤效应可被观测。在此，我们通过磁输运和温度依赖测量，实验证明了六层菱方石墨烯莫尔超晶格中的近藤相互作用。随着磁场的增加，磁阻在临界磁场B_c处表现出先增后减的转变，而霍尔电阻R_xy在B_c附近发生符号反转。此外，随着温度降低，纵向电阻R_xx先对数增加，随后按T^2行为下降，表明向重费米子液体的转变。这些行为可以通过磁场或温度诱导的近藤单态破坏来一致解释，该破坏释放了先前束缚于局域矩的载流子，从而增强电导并改变主导载流子类型。进一步地，我们的结果表明近藤相互作用可通过载流子密度n和位移电场D连续调节，并暗示近藤绝缘态的出现。我们的发现为莫尔工程平带系统中的近藤效应提供了深刻见解，为探索奇异关联量子相铺平了道路。
英文摘要
Kondo effect in strongly correlated systems arises from the antiferromagnetic coupling between itinerant conduction electrons and localized magnetic moments, giving rise to a variety of exotic quantum phenomena. Two-dimensional moiré superlattice systems provide a highly tunable platform featuring topological flat bands, where Wannier orbitals are spatially confined by the periodic moiré potential and serve as localized magnetic moments, enabling the observable Kondo effect. Here we experimentally demonstrate Kondo interactions in hexalayer rhombohedral graphene moiré superlattices through magneto-transport and temperature-dependent measurements. With increasing magnetic field, the magnetoresistance exhibits an increase-decrease transition across a critical field B_c, while the Hall resistance R_xy undergoes a sign reversal near B_c. Moreover, as temperature decreases, the longitudinal resistance R_xx first increases logarithmically and then decreases following a T^2 behavior, indicating a transition to heavy fermion liquid. These behaviors can be consistently explained by the breakdown of Kondo singlets induced by either magnetic field or temperature, which liberates carriers previously bound to localized moments, thereby enhancing conductivity and altering the dominant carrier type. Furthermore, our results demonstrate that the Kondo interaction can be continuously tuned by both carrier density n and displacement electric field D, and suggest the emergence of a Kondo insulating state. Our findings provide deep insight into the Kondo effect in moiré engineered flat-band systems, paving the path for exploring exotic correlated quantum phases.
发表机构
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University（北京大学物理学院介观物理国家重点实验室和纳米光电前沿科学中心）
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology（北京理工大学物理学院量子物理中心、先进光电子量子架构与测量教育部重点实验室）
- Research Center for Electronic and Optical Materials, National Institute for Material Sciences（物质材料研究机构电子与光学材料研究中心）
- Research Center for Materials Nanoarchitectonics, National Institute for Material Sciences（物质材料研究机构材料纳米结构研究中心）
- Hefei National Laboratory（合肥国家实验室）
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