Article
Physics, Multidisciplinary
Zhen Ma, Shuai Li, Meng-Meng Xiao, Ya-Wen Zheng, Ming Lu, Haiwen Liu, Jin-Hua Gao, X. C. Xie
Summary: We report a new family of twisted few layer graphite, which has distinct moire flat band structures that can be highly tuned. The moire band structure strongly depends on the layer number of the graphite, and near the magic angle, it exhibits two nearly flat bands coexisting with dispersive bands. This property enhances the possible superconductivity and also indicates that it is a novel topological flat band system.
FRONTIERS OF PHYSICS
(2023)
Article
Chemistry, Physical
Shaofei Li, Haihong Zheng, Junnan Ding, Biao Wu, Jun He, Zongwen Liu, Yanping Liu
Summary: In this study, a dynamic local deformation of twisted WS2-WSe2 heterostructures was achieved at room temperature using a diamond anvil cell (DAC), enabling in-situ dynamic modulation of moire potential. The deformation of the twisted heterostructure increased the moire potential, causing a red shift of the moire exciton resonance. It also observed a red shift of the intralayer exciton resonance and a blue shift of the interlayer excitons of twisted WS2-WSe2 heterostructures.
Article
Materials Science, Multidisciplinary
Long-Jing Yin, Ling-Hui Tong, Yue-Ying Zhou, Yang Zhang, Yuan Tian, Li Zhang, Lijie Zhang, Zhihui Qin
Summary: By studying the local electronic properties of magic-angle twisted bilayer graphene, we observe a breakdown of the flat bands at the sample terminated edge. We find that complete moiré spots are necessary for the generation of effective flat bands in twisted bilayer graphene.
Article
Materials Science, Multidisciplinary
Jiseon Shin, Bheema Lingam Chittari, Yunsu Jang, Hongki Min, Jeil Jung
Summary: In this study, we investigate the electronic structure of alternating-twist triple Bernal-stacked bilayer graphene (t3BG) by varying interlayer coupling, twist angle, interlayer potential difference, and sliding vector. We find that under certain parameters, the bands can flatten down to low energy levels, facilitating the formation of correlation-driven gaps.
Article
Multidisciplinary Sciences
En Li, Jin-Xin Hu, Xuemeng Feng, Zishu Zhou, Liheng An, Kam Tuen Law, Ning Wang, Nian Lin
Summary: The authors demonstrate the emergence of multiple ultra-flat electronic bands in twisted bilayer WSe2 using scanning tunneling microscopy and spectroscopy, indicating the potential for further study of exotic correlated phases in TB-TMDs.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Physical
Biao Wu, Haihong Zheng, Shaofei Li, Chang-Tian Wang, Junnan Ding, Jun He, Zongwen Liu, Jian-Tao Wang, Yanping Liu
Summary: The discovery of moire-related properties in the vertical stacking of two different monolayers has attracted significant attention recently. By introducing small twist angles in TMD heterostructures, moire potentials emerge, providing a platform for studying strong electron interactions. While there has been extensive research on moire excitons in twisted bilayer superlattices, capturing and studying moire excitons in homostructure superlattices with layer-coupling effects remain elusive.
Article
Physics, Multidisciplinary
Guoyu Luo, Lu Wen, Xinyu Lv, Zhiqiang Li
Summary: This theoretical study investigates the band structure and optical conductivity of twisted double bilayer graphene under an applied vertical electric field. Different arrangements and electric field strengths lead to distinct optical properties, with observable differences in energy gaps and absorption edges. Tuning the electric field can achieve extremely narrow bandwidths for flat bands, showcasing potential for tunable optical properties in twisted double bilayer graphene.
Review
Chemistry, Multidisciplinary
Yanping Liu, Cheng Zeng, Juan Yu, Jiahong Zhong, Bo Li, Zhengwei Zhang, Zongwen Liu, Zhiming M. Wang, Anlian Pan, Xidong Duan
Summary: Recent advances in moire superlattices and moire excitons have attracted attention in optoelectronics and materials research. However, lagging theoretical development and inefficient processing technologies limit their potential applications. Continued research is likely to lead to breakthroughs and innovations in solid-state physics and materials science.
CHEMICAL SOCIETY REVIEWS
(2021)
Article
Chemistry, Physical
Min Long, Pierre A. Pantaleon, Zhen Zhan, Francisco Guinea, Jose Angel Silva-Guillen, Shengjun Yuan
Summary: This study investigates the heterostructures of twisted bilayer graphene (TBG) and hexagonal boron nitride (hBN) using an atomistic tight-binding model and semi-classical molecular dynamics. The hBN substrate significantly affects the band structure of TBG, inducing mass gaps and pseudo-magnetic fields that break layer degeneracy. However, the degeneracy can be recovered with a second hBN layer. Real-space tight-binding model combined with semi-classical molecular dynamics is shown to be a powerful tool for studying electronic properties of moire heterostructures.
NPJ COMPUTATIONAL MATERIALS
(2022)
Article
Physics, Multidisciplinary
Tawfiqur Rakib, Pascal Pochet, Elif Ertekin, Harley T. Johnson
Summary: The study reveals that the partially filled band and symmetry breaking phenomena in magic-angle twisted bilayer graphene can be explained by the large out-of-plane displacement induced by the interlayer twist. This observation provides insights into the exotic electronic properties in magic-angle twisted bilayer graphene and may offer a strategy to mitigate the effects of disorder.
COMMUNICATIONS PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Rahul Debnath, Shaili Sett, Rabindra Biswas, Varun Raghunathan, Arindam Ghosh
Summary: Van der Waals (vdW) heterostructure is a metamaterial where multiple layers of 2D materials are vertically aligned with controlled misorientation. The twist angle between layers is crucial for changing the electronic band structure of the superlattice, and the fabrication process requires precise knowledge of the atomic structure and orientation. The presented method uses an optical microscope for edge identification, achieving controlled transfer of twisted materials with high yield and accuracy.
Article
Chemistry, Multidisciplinary
Shengdan Tao, Xuanlin Zhang, Jiaojiao Zhu, Pimo He, Shengyuan A. Yang, Yunhao Lu, Su-Huai Wei
Summary: A new design principle is proposed to achieve low-energy ultra-flat bands with increased twist angles in intertwined bilayers of two-dimensional materials, providing a new route for investigating strong electron correlations.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Multidisciplinary Sciences
Manabendra Kuiri, Christopher Coleman, Zhenxiang Gao, Aswin Vishnuradhan, Kenji Watanabe, Takashi Taniguchi, Jihang Zhu, Allan H. MacDonald, Joshua Folk
Summary: This study discovered a strong anomalous Hall effect in twisted double bilayer graphene, suggesting the breaking of time reversal symmetry due to orbital ferromagnetism. Gate voltages applied to the device can tune both the flatness and topology of the electronic bands, providing an unusual level of experimental control.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Multidisciplinary
Bing Liu, Lede Xian, Haimen Mu, Gan Zhao, Zhao Liu, Angel Rubio, Z. F. Wang
Summary: This study predicts the potential existence of a 2D second-order topological insulator in twisted bilayer materials, with unique features such as a non-zero bulk topological index, gapped topological edge states, and in-gap topological corner states. This phenomenon is not only observed in a wide range of twist angles, but also shows robustness to microscopic structure disorder and twist centers, facilitating experimental measurements.
PHYSICAL REVIEW LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Shivesh Pathak, Tawfiqur Rakib, Run Hou, Andriy Nevidomskyy, Elif Ertekin, Harley T. Johnson, Lucas K. Wagner
Summary: The study suggests that the magic angle shifts to slightly lower angles than often quoted, showing isolated flat bands appearing for rigidly rotated graphene layers, with enhancement of the flat bands when the layers are allowed to distort. Study of orbital localization supports the emergence of fragile topology in the isolated flat bands without the need for lattice relaxation.
Article
Physics, Multidisciplinary
Humian Zhou, Hailong Li, Dong-Hui Xu, Chui-Zhen Chen, Qing-Feng Sun, X. C. Xie
Summary: This study systematically investigates the surface transport of a semimagnetic topological insulator and reveals the direct relationship between the half-quantized Hall conductance and the half-quantized chiral current along the edge of a strongly dephasing metal.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Junjie Zeng, Qingming Li, Xun Yang, Dong-Hui Xu, Rui Wang
Summary: Recent studies have found unexpected chiral flux phases in quasi-2D kagome superconductors AV(3)Sb(5), which are associated with the spontaneous time-reversal symmetry breaking in charge density wave states. The researchers have further investigated the unique edge state properties of these chiral flux phases and found that they are consistent with the Bogoliubov-de Gennes Chern numbers.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Rui Chen, Hai-Peng Sun, Bin Zhou, Dong-Hui Xu
Summary: The quantum anomalous Hall effect is characterized by a quantized Hall resistance and vanishing longitudinal resistance. Many experiments have reported the quantization of Hall resistance, but always accompanied by a non-vanishing longitudinal resistance. This resistance exhibits a universal exponential decay with the increase in magnetic field. Our theory proposes that the coupling of chiral edge states, not properly evaluated in previous theories, can explain this non-vanishing longitudinal resistance.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2023)
Article
Materials Science, Multidisciplinary
Xiong-Tao Peng, Fang Lin, Liang Chen, Lin Li, Dong-Hui Xu, Jin-Hua Sun
Summary: In this study, we investigate the correlation effects of magnetic impurities influenced by the k-cubic Rashba spin-orbit coupling (SOC) using the variational method and Hirsch-Fye quantum Monte Carlo simulations. We find that even a small cubic Rashba term can significantly modify the band structure and induce a Van Hove singularity, leading to tunable single impurity local moments. The spin-spin correlation between the magnetic impurity and conduction electrons exhibits unique three- or sixfold rotational symmetry due to the triple winding of spins with a 2 pi rotation of k, which distinguishes the cubic Rashba SOC from the normal k-linear Rashba term. Additionally, we observe twisted features in the carrier-mediated Ruderman-Kittel-Kasuya-Yosida interactions between two magnetic impurities, with ferromagnetic diagonal terms dominating at close distances and important off-diagonal terms at long distances.
Article
Materials Science, Multidisciplinary
Zi-Ming Wang, Rui Wang, Jin-Hua Sun, Ting-Yong Chen, Dong-Hui Xu
Summary: Floquet engineering, a concept of manipulating topological phases of matter by periodic driving, is used to study higher-order topological Dirac semimetals under circularly polarized light. The driven system exhibits Floquet Weyl semimetal phases with hybrid-order topology, characterized by a k-dependent quantized quadrupole moment and a k-dependent Chern number. These phases support hinge Fermi arc and topological surface Fermi arc states. The findings have the potential to be experimentally verified given the recent proposals of higher-order topological Dirac semimetal materials.
Article
Materials Science, Multidisciplinary
Meng Zeng, Dong-Hui Xu, Zi-Ming Wang, Lun-Hui Hu
Summary: This study investigates the effects of spin-symmetry pairing and atomic spin-orbit coupling on superconductivity in a two-band superconductor with two nearly degenerate orbitals. It discovered that the spin-orbit coupling can lead to the realization of topological chiral or helical Majorana edge states without external magnetic fields or Zeeman fields, and a spin-polarized superconducting state when time-reversal symmetry is spontaneously broken.
Article
Materials Science, Multidisciplinary
Shi-Nan Chen, Jin-Hua Sun, Zhen-Hua Wang, Wei Su, Dong-Hui Xu, Hong-Gang Luo, Lin Li
Summary: We investigate the Kondo effect in type-II Ising superconductors with a single magnetic impurity. The type-II Ising spin-orbit coupling in these materials generates out-of-plane effective Zeeman fields, protecting interorbital superconducting pairing states against in-plane magnetic fields. The behavior of spin-induced Yu-Shiba-Rusinov bound states and low-temperature magnetic susceptibility shows that the spin-orbit coupling suppresses the Kondo screening of the magnetic moment.
Article
Materials Science, Multidisciplinary
Chun-Bo Hua, Feiping Xiao, Zheng-Rong Liu, Jin-Hua Sun, Jin-Hua Gao, Chui-Zhen Chen, Qingjun Tong, Bin Zhou, Dong-Hui Xu
Summary: In this study, twisted bilayer honeycomb magnets were found to host second-order topological magnon insulators (SOTMIs) without fine-tuning. These SOTMIs exhibit unique, topologically protected magnon corner states that go beyond conventional bulk-boundary correspondence. The interlayer exchange coupling in the bilayer system plays a significant role in determining its higher-order topology.
Article
Materials Science, Multidisciplinary
Zheng Qin, Dong-Hui Xu, Zhen Ning, Rui Wang
Summary: In this study, we demonstrate the realization of one-dimensional chiral anomaly in a generalized Su-Schrieffer-Heeger model, which exhibits the half-integer quantization of a winding number. We also investigate the evolution of the system under on-site and bond disorders and propose a strategy to detect the half-integer quantization.
Article
Materials Science, Multidisciplinary
Zhen Ning, Xianyong Ding, Dong-Hui Xu, Rui Wang
Summary: In this study, we propose an anisotropic Dirac semimetal model which can be realized on a deformed honeycomb lattice subjected to a magnetic flux. The results show that the nearly half-integer quantization of Hall conductivity can exist in a wide region of disorder in this topological semimetallic phase.
Article
Materials Science, Multidisciplinary
Wen-Bo Dai, Hailong Li, Dong-Hui Xu, Chui-Zhen Chen, X. C. Xie
Summary: In this study, a new type of Hall effect called quantum anomalous layer Hall effect (QALHE) is observed in the even-layered two-dimensional antiferromagnetic MnBi2Te4. The quantized Hall conductance of QALHE can be controlled by a vertical electric field and can change sign with electric-field reversal in both the even-layered antiferromagnetic phase and the ferromagnetic phase. These findings offer a promising approach to electrically engineer Berry curvature monopoles and quantized-layered transport in topological magnets.
Article
Materials Science, Multidisciplinary
Zhen Ning, Bo Fu, Dong-Hui Xu, Rui Wang
Summary: This paper theoretically investigates topological phase transitions and establishes the quadrupole topological insulator (QTI) phase in a periodically driven system with disorder. The results show that the Floquet QTI phase can emerge from a topologically trivial band structure driven by elliptically polarized irradiation, and an intriguing QTI phase which necessitates the simultaneous presence of disorder and periodic driving can be revealed starting from a pure and static system with trivial topology. Furthermore, it is revealed that particle-hole symmetry is sufficient to protect the QTI.
Article
Materials Science, Multidisciplinary
Qiu-Yue Xu, Feng Liu, Chui-Zhen Chen, Dong-Hui Xu
Summary: Breaking Hermiticity in topological systems leads to intriguing phenomena, such as exceptional topology and the non-Hermitian skin effect. This work focuses on a non-Hermitian topological crystalline insulator on a Kekule texture-modulated honeycomb lattice with balanced gain and loss. The study finds that the gaplessness of the topological edge states in the non-Hermitian system is insensitive to edge geometries under moderate strength of gain and loss.
Article
Materials Science, Multidisciplinary
Xiu-Li Du, Rui Chen, Rui Wang, Dong-Hui Xu
Summary: In this study, we investigated the tunable Floquet states in a periodically driven higher-order nodal-line semimetal with both spatial inversion and time-reversal symmetries. We found that circularly polarized light can induce Floquet Weyl semimetal states in the higher-order nodal-line semimetal and that the location of Weyl nodes and the curvature of surface Fermi arcs can be tuned by adjusting the propagation direction and incident angle of light.
