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Multidisciplinary Sciences
Jiaqi Cai, Eric Anderson, Chong Wang, Xiaowei Zhang, Xiaoyu Liu, William Holtzmann, Yinong Zhang, Fengren Fan, Takashi Taniguchi, Kenji Watanabe, Ying Ran, Ting Cao, Liang Fu, Di Xiao, Wang Yao, Xiaodong Xu
Summary: This study reports experimental evidence of fractional quantum anomalous Hall (FQAH) states in twisted MoTe2 bilayers. By using magnetic circular dichroism measurements and trion photoluminescence as a sensor, the researchers demonstrate the presence of FQAH states by observing the corresponding dispersion curves and linear shifts. These topological states can be electrically driven into topologically trivial states and provide a platform for exploring fractional excitations.
Article
Physics, Multidisciplinary
Daniel Failde, Daniel Baldomir
Summary: In relativistic quantum formalism, second-order corrections due to magnetic fields in two-dimensional topological and Chern insulators play a crucial role in determining the zero-field diamagnetic susceptibility of non-zero Berry curvature systems. These corrections become relevant at relatively low fields and unveil additional contributions from the magnetic field.
NEW JOURNAL OF PHYSICS
(2021)
Article
Chemistry, Physical
Shuang Wu, Zhenyuan Zhang, K. Watanabe, T. Taniguchi, Eva Y. Andrei
Summary: In magic-angle twisted bilayer graphene, doping-induced Lifshitz transitions and van Hove singularities lead to the emergence of correlation-induced gaps and topologically non-trivial subbands. With the presence of a magnetic field, quantized Hall plateaus reveal the subband topology and signal the emergence of Chern insulators with Chern numbers. Additionally, a van Hove singularity at a filling of 3.5 suggests the possibility of a fractional Chern insulator, accompanied by a crossover from low-temperature metallic to high-temperature insulating behavior.
Article
Materials Science, Multidisciplinary
Lukas Wawer, Michael Fleischhauer
Summary: The study extends the concept of ensemble geometric phase to mixed states in two-dimensional band structures, introducing a proper Chern number calculation method for various types of states. The Chern number can be calculated through the ground-state Berry curvature of a fictitious Hamiltonian that breaks time-reversal symmetry.
Article
Multidisciplinary Sciences
Yonglong Xie, Andrew T. Pierce, Jeong Min Park, Daniel E. Parker, Eslam Khalaf, Patrick Ledwith, Yuan Cao, Seung Hwan Lee, Shaowen Chen, Patrick R. Forrester, Kenji Watanabe, Takashi Taniguchi, Ashvin Vishwanath, Pablo Jarillo-Herrero, Amir Yacoby
Summary: Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states and have been recently observed in magic-angle twisted BLG at low magnetic field. The appearance of these states at 5 T is accompanied by the disappearance of nearby topologically trivial charge density wave states.
Article
Physics, Multidisciplinary
Mahmut Sait Okyay, Shunsuke A. Sato, Kun Woo Kim, Binghai Yan, Hosub Jin, Noejung Park
Summary: The second harmonic optical responses of insulators to sub-bandgap light are found to be delicately associated with the interband Berry curvature dipole. Adjustments of the dipole or other multipole structures of the Berry curvature texture can detect the consequences of symmetry lowering.
COMMUNICATIONS PHYSICS
(2022)
Article
Physics, Multidisciplinary
Vidhi Shingla, Haoyun Huang, Ashwani Kumar, Loren N. Pfeiffer, Kenneth W. West, Kirk W. Baldwin, Gabor A. Csathy
Summary: Composite fermions can form bubbles that order into a lattice. The re-entrance of the fractional quantum Hall effect is associated with a bubble phase with two composite fermion quasiparticles per bubble. This observation demonstrates the existence of a new class of strongly correlated topological phases driven by clustering and charge ordering of emergent quasiparticles.
Article
Chemistry, Physical
Janusz E. Jacak
Summary: The recent research focuses on the classification of 2D electron states induced by different mappings of the planar Brillouin zone, as well as the classification of various phases of multi-electron homotopy patterns induced by Coulomb interaction. The presence of long-range quantum entanglement is essential for homotopy correlated phases, which are topologically protected and immune to local crystal field and disorder. The classification of homotopy long-range correlated phases is based on homotopy invariants and has been demonstrated through experimental observations in various materials.
Article
Physics, Multidisciplinary
Subhajit Sinha, Pratap Chandra Adak, Atasi Chakraborty, Kamal Das, Koyendrila Debnath, L. D. Varma Sangani, Kenji Watanabe, Takashi Taniguchi, Umesh Waghmare, Amit Agarwal, Mandar M. Deshmukh
Summary: The topological aspects of the electron wave function, including the Berry curvature and Chern number, play a crucial role in determining the physical properties of materials. Twisted double bilayer graphene offers a tunable system to study topological transitions and has potential applications in next-generation Berry-curvature-based memory devices. Furthermore, the strain-induced Berry curvature dipole can be used to detect topological transitions in the bands.
Article
Multidisciplinary Sciences
Qicheng Zhang, Li He, Eugene J. Mele, Bo Zhen, A. T. Charlie Johnson
Summary: Integrated phononics plays a crucial role in fundamental physics and technology. This study investigates the use of piezomagnetic materials to break time-reversal symmetry and achieve topological phases and non-reciprocal devices. The authors develop a theoretical framework that combines linear elasticity with Maxwell's equations and demonstrate the existence of phononic Chern insulators based on piezomagnetism.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Multidisciplinary
Lucien Jezequel, Pierre Delplace
Summary: We propose a non-Hermitian generalization of the correspondence between spectral flow and topological charges of band crossing points. This is achieved by deforming an Hermitian model while preserving its analytical index. We establish a relation between the non-Hermitian spectral flows and a generalized Chern number, which is shown to be equal to the Hermitian case when a line gap exists. We demonstrate the homotopic invariance of both the non-Hermitian Chern number and the spectral flow index, highlighting their topological nature. In the absence of a line gap, the system still exhibits a spectral flow that can be captured using an emergent pseudo-Hermitian symmetry.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Chunli Huang, Nemin Wei, Allan H. MacDonald
Summary: This study explores the quantized anomalous Hall effect in graphene multilayers with flat moire minibands, and suggests a current-driven mechanism for reversing the sign of the Hall effect in these Chern insulators.
PHYSICAL REVIEW LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Tomas Rauch, Thomas Olsen, David Vanderbilt, Ivo Souza
Summary: The paper discusses the topology of electronic states in band insulators with mirror symmetry, classifying them through the mirror Chern number and Z(2) index. By examining the Wannier functions and band structures, the relationship between mirror Chern number and axion Z(2) index is established. The study uses ab initio calculations for SnTe and tight-binding calculations for a toy model to illustrate the formalism.
Article
Materials Science, Multidisciplinary
Yi-Xin Xiao, C. T. Chan
Summary: This study investigates the bulk-boundary correspondence in a Chern insulator model with non-Hermitian skin effect, using the biorthogonal approach and non-Bloch approach to suppress the skin effect. The biorthogonal inverse participation ratio and non-Bloch Chern number are utilized as metrics and tools for predicting topological features. Moreover, the occurrence of crossing degeneracies between bulk and edge bands enriches the localization behavior of edge states.
Article
Physics, Applied
Xin Yang, Yanqing Shen, Jiajia Liu, Lingling Lv, Min Zhou, Yu Zhang, Xianghui Meng, Zhongxiang Zhou, Yangdong Zheng
Summary: The topologically nontrivial phase and quantum anomalous Hall (QAH) effect were predicted in the ferromagnetic non-Dirac half-metal N2Pd4S6 monolayer using first-principles calculations. The N2Pd4S6 monolayer prefers out-of-plane magnetization and exhibits a Curie temperature of similar to 80 K due to dual double-exchange interaction. The introduction of magnetic exchange and spin-orbit coupling enables the realization of the topologically nontrivial phase and QAH state, as well as the unique quantum anomalous valley Hall (QAVH) effect induced by compressive strain.
APPLIED PHYSICS LETTERS
(2023)
News Item
Physics, Multidisciplinary
Steven H. Simon
Article
Physics, Multidisciplinary
Glenn Wagner, Dung X. Nguyen, Dmitry L. Kovrizhin, Steven H. Simon
PHYSICAL REVIEW LETTERS
(2019)
Article
Physics, Multidisciplinary
Glenn Wagner, Dung X. Nguyen, Steven H. Simon
PHYSICAL REVIEW LETTERS
(2020)
Article
Physics, Multidisciplinary
Felix Flicker, Steven H. Simon, S. A. Parameswaran
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Physics, Multidisciplinary
Steven H. Simon, Bernd Rosenow
PHYSICAL REVIEW LETTERS
(2020)
Article
Physics, Multidisciplinary
Yves H. Kwan, Yichen Hu, Steven H. Simon, S. A. Parameswaran
Summary: The study reveals the topological features of neutral particle-hole pair excitations and their impact on the bound states in correlated QAH insulators. This results in the formation of topological exciton bands with robust features. The research also applies these ideas to broken-symmetry spontaneous QAH insulators in magic-angle twisted bilayer graphene with substrate alignment.
PHYSICAL REVIEW LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Steven H. Simon, Mark S. Rudner
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Materials Science, Multidisciplinary
Glenn Wagner, Dung X. Nguyen, Steven H. Simon
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Materials Science, Multidisciplinary
Dung X. Nguyen, Glenn Wagner, Steven H. Simon
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Materials Science, Multidisciplinary
Steven H. Simon, Matteo Ippoliti, Michael P. Zaletel, Edward H. Rezayi
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Materials Science, Multidisciplinary
Glenn Wagner, Dung X. Nguyen, Dmitry L. Kovrizhin, Steven H. Simon
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Materials Science, Multidisciplinary
J-R Soh, F. de Juan, M. G. Vergniory, N. B. M. Schroeter, M. C. Rahn, D. Y. Yan, J. Jiang, M. Bristow, P. A. Reiss, J. N. Blandy, Y. F. Guo, Y. G. Shi, T. K. Kim, A. McCollam, S. H. Simon, Y. Chen, A. Coldea, A. T. Boothroyd
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Physics, Multidisciplinary
Henrik S. Roising, Thomas Scaffidi, Felix Flicker, Gunnar F. Lange, Steven H. Simon
PHYSICAL REVIEW RESEARCH
(2019)
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Physics, Multidisciplinary
Henrik Schou Roising, Roni Ilan, Tobias Meng, Steven H. Simon, Felix Flicker
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Materials Science, Multidisciplinary
Abishek K. Kulshreshtha, Arijeet Pal, Thorsten B. Wahl, Steven H. Simon