We explore a novel mechanism for control of periodicity in persistent current in a twisted normal metal loop threaded by a magnetic flux $ϕ$. A simple tight-binding model is used to describe the system. Quite interestingly we see that, depending on the number of twist $p$, the persistent current exhibits $ϕ_0/p$ ($ϕ_0=ch/e$, the elementary flux-quantum) periodicity. Such fractional periodicity provides a new finding in the study of persistent current.
Although much progress has been made on the physics of magic angle twisted bilayer graphene at integer fillings, little attention has been given to fractional fillings. Here we show that the three-peak structure of Wannier orbitals, dictated by the symmetry and topology of flat bands, facilitates the emergence of a novel state at commensurate fractional filling of $ν= n \pm 1/3$. We dub this state a "fractional correlated insulator". Specifically for the filling of $\pm 1/3$ electrons per moiré unit cell, we show that short-range interactions alone imply an approximate extensive entropy due to…
Optical signatures of -1/3 fractional quantum anomalous Hall state in twisted MoTe2
Nanyang Technological University（南洋理工大学）；Nanjing University of Aeronautics and Astronautics（南京航空航天大学）；Nanjing Tech University（南京工业大学）；National Institute for Materials Science（国立材料研究所）
Persistent currents, whirlpools, and local Chern markers in twisted TMD Chern insulators
Scuola Normale Superiore（比萨高等师范学院）；International School for Advanced Studies (SISSA)（国际高等研究院）；Dipartimento di Fisica dell’Università di Pisa（比萨大学物理系）；Istituto Nanoscienze – CNR（意大利国家研究委员会纳米科学研究所）；Department of Physics, Harvard University（哈佛大学物理学系）
Fractional High-Chern Insulator in Twisted Rhombohedral Graphene
International Center for Quantum Materials, School of Physics, Peking University（北京大学物理学院量子材料国际中心）；State Key Laboratory for Mesoscopic Physics, Frontiers Science Centre 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纳米光电子前沿科学中心）；Research Center for Electronic and Optical Materials, National Institute of Material Sciences（物质材料研究机构电子光学材料研究中心）；Research Center for Materials Nanoarchitectonics, National Institute of Material Sciences（物质材料研究机构材料纳米构造研究中心）；Interdisciplinary Center for Theoretical Physics and Information Sciences, Fudan University（复旦大学理论物理与信息科学交叉中心）；Hefei National Laboratory（合肥国家实验室）；Collaborative Innovation Center of Quantum Matter（量子物质协同创新中心）
We predict twisted double bilayer graphene to be a versatile platform for the realization of fractional Chern insulators readily targeted by tuning the gate potential and the twist angle. Remarkably, these topologically ordered states of matter, including spin singlet Halperin states and spin polarized states in Chern number $\mathcal C=1$ and $\mathcal{C}= 2$ bands, occur at high temperatures and without the need for an external magnetic field.
We show that the flat bands in the chiral model of magic-angle twisted bilayer graphene remain exactly flat in the presence of a perpendicular magnetic field. This is shown by an exact mapping between the model and the lowest Landau level wavefunctions at an effective magnetic field, in which the external field is either augmented or reduced by one flux quantum per unit cell. When the external field reaches one flux quantum per unit cell, the model exhibits a topological phase transition. These findings allow us to analyze a Jain-series of Fractional Chern Insulators states in the exactly flat…
We perform an extensive exact diagonalization study of interaction driven insulators in spin- and valley-polarized moiré flat bands of twisted bilayer graphene aligned with its hexagonal boron nitride substrate. In addition to previously reported fractional Chern insulator phases, we provide compelling evidence for competing charge-density-wave phases at multiple fractional fillings of a realistic single-band model. A thorough analysis at different interlayer hopping parameters, motivated by experimental variability, and the role of kinetic energy at various Coulomb interaction strengths highl…
Pressure-Tunable Generalized Wigner Crystal and Fractional Chern Insulator in twisted MoTe$_2$
Beijing Institute of Technology（北京理工大学）；Beijing Key Laboratory of Quantum Matter State Control and Ultra-Precision Measurement Technology（北京量子物质态调控与超精密测量技术重点实验室）
Fractional Chern insulators in alternating twisted multilayer MoTe$_{2}$
Huazhong University of Science and Technology（华中科技大学）；Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology（华中科技大学武汉国家高能磁场中心）；Hubei Fundamental Research Center for Physics（湖北省物理基础研究中心）
Quantum Hall (QH) interferometry provides an archetypal platform for the experimental realization of braiding statistics of fractional QH states. However, the complexity of observing fractional statistics requires phase coherence over the length of the interferometer, as well as suppression of Coulomb charging energy. Here, we demonstrate a new type of QH interferometer based on marginally twisted bilayer graphene (mtBLG), with a twist angle $θ$ $\approx$ $0.16$ $^{\circ}$. With the device operating in the QH regime, we observe distinct signatures of electronic Fabry-Pérot (FP) and Aharonov-Bo…
Three-Dimensional Non-Foliated Fractional Quantum Hall Phases with Irrational Anyons in Twisted van der Waals Multilayers
Pohang University of Science and Technology（浦项科技大学）；Daegu Gyeongbuk Institute of Science and Technology (DGIST)（大邱庆北科学技术院）；Korea Advanced Institute of Science and Technology（韩国科学技术院）；Institute for Basic Science（基础科学研究院）
Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states that may provide a new avenue toward manipulating non-abelian excitations. Early theoretical studies have predicted their existence in systems with energetically flat Chern bands and highlighted the critical role of a particular quantum band geometry. Thus far, however, FCI states have only been observed in Bernal-stacked bilayer graphene aligned with hexagonal boron nitride (BLG/hBN), in which a very large magnetic field is responsible for the existence of the Chern bands, precluding the realization of …
Magnetic-field response of generalized Wigner crystals in twisted MoTe$_2$
Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Department of Physics, University of Washington（华盛顿大学物理系）；Department of Materials Science and Engineering, University of Washington（华盛顿大学材料科学与工程系）；Research Center for Materials Nanoarchitectonics, National Institute for Materials Science（物质材料研究机构材料纳米架构研究中心）；Research Center for Electronic and Optical Materials, National Institute for Materials Science（物质材料研究机构电子与光学材料研究中心）
Twist-angle-dependent quantum phase diagrams in twisted bilayer MoTe2
State Key Laboratory of Micro-nano Engineering Science, Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院微纳工程科学国家重点实验室人工结构量子控制教育部重点实验室）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学李政道研究所）；Department of Physics, Hong Kong University of Science and Technology（香港科技大学物理系）；State Key Laboratory of Surface Physics and Department of Physics, Fudan University（复旦大学表面物理国家重点实验室物理系）；Department of Physics and Astronomy, University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校物理与天文学系）；Research Center for Electronic and Optical Materials, National Institute for Materials Science（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 Materials Science（物质材料研究机构材料纳米构造研究中心）；Hefei National Laboratory（合肥国家实验室）；Shanghai Research Center for Quantum Sciences（上海量子科学研究与交流中心）；Max Planck Institute for Chemical Physics of Solids（德国马克斯·普朗克固体化学物理研究所）；Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校明浩高电气工程和计算机科学系）；New Cornerstone Science Laboratory, Fudan University（复旦大学新基石科学实验室）
Superconductivity Proximate to Non-Abelian Fractional Spin Hall Insulator in Twisted Bilayer MoTe$_2$
Pohang University of Science and Technology（浦项科技大学）；Ulsan National Institute of Science and Technology（蔚山科学技术院）；Daegu Gyeongbuk Institute of Science and Technology (DGIST)（大邱庆北科学技术院）；Korea Advanced Institute of Science and Technology（韩国科学技术院）；Institute for Basic Science（基础科学研究院）
Utilizing the realistic continuum description of twisted bilayer MoTe2 and many-body exact diagonalization calculation, we establish that the second moiré band of twisted bilayer MoTe2, at a small twist angle of approximately 2°, serves as an optimal platform for achieving the long-sought non-Abelian fractional quantum anomalous Hall states without the need for external magnetic fields. Across a wide parameter range, our exact diagonalization calculations reveal that the half-filled second moiré band demonstrates the ground state degeneracy and spectral flows, which are consistent with the pfa…
Fractional Chern Insulators Transition in Non-ideal Flat Bands of Twisted Mono-bilayer Graphene
State Key Laboratory of Semiconductor Physics and Chip Technologies, Institute of Semiconductors, Chinese Academy of Sciences（中国科学院半导体研究所半导体物理与芯片技术国家重点实验室）；Center for Quantum Matter, Zhejiang University（浙江大学量子物质中心）；College of Materials Science and Opto-electronic Technology, University of Chinese Academy of Sciences（中国科学院大学材料科学与光电技术学院）
Moiré flatbands, occurring, e.g., in twisted bilayer graphene at magic angles, have attracted ample interest due to their high degree of experimental tunability and the intriguing possibility of generating novel strongly interacting phases. Here we consider the core problem of Coulomb interactions within fractionally filled spin and valley polarized Moiré flatbands and demonstrate that the dual description in terms of holes, which acquire a nontrivial hole dispersion, provides key physical intuition and enables the use of standard perturbative techniques for this strongly correlated problem. I…
The long wavelength moiré superlattices in twisted 2D structures have emerged as a highly tunable platform for strongly correlated electron physics. We study the moiré bands in twisted transition metal dichalcogenide homobilayers, focusing on WSe$_2$, at small twist angles using a combination of first principles density functional theory, continuum modeling, and Hartree-Fock approximation. We reveal the rich physics at small twist angles $θ<4^\circ$, and identify a particular magic angle at which the top valence moiré band achieves almost perfect flatness. In the vicinity of this magic angle, …
