Article
Chemistry, Multidisciplinary
Zhiming Xu, Wenhui Duan, Yong Xu
Summary: In this study, we constructed a first-principles database for quantum anomalous Hall (QAH) materials and explored the microscopic mechanisms that determine their properties. We found that the Coulomb exchange, which is usually neglected, plays a strong role in a large class of QAH materials and is key to resolving experimental puzzles. Additionally, we identified simple indicators for property evaluation and suggested material design strategies to control QAH chirality and gap. This work is valuable for future research in magnetic topological physics and materials.
Article
Nanoscience & Nanotechnology
Yinong Zhou, Gurjyot Sethi, Hang Liu, Zhengfei Wang, Feng Liu
Summary: This article proposes theoretical concepts and models to describe the excited quantum anomalous Hall effect and quantum spin Hall effect generated by the dissociation of an excitonic insulator state. These effects are based on the nontrivial band topology and complete population inversion in 2D materials, and have important scientific significance and potential applications.
Article
Chemistry, Multidisciplinary
Hee Taek Yi, Deepti Jain, Xiong Yao, Seongshik Oh
Summary: Researchers have developed a platform that overcomes limitations of the quantum anomalous Hall effect (QAHE), enabling observation at higher temperatures without the need for electric-field-effect gating. By introducing a CrO x capping layer, the material's properties are improved, allowing for broader applications of QAHE.
Article
Chemistry, Multidisciplinary
Tengfei Cao, Ding-Fu Shao, Kai Huang, Gautam Gurung, Evgeny Y. Tsymbal
Summary: Based on symmetry analyses and density-functional calculations, this study explores the emergence of the anomalous Hall effect (AHE) in antiferromagnetic MnBi2Te4 films assembled by polar layer stacking. Breaking PT symmetry in an MnBi2Te4 bilayer produces a magnetoelectric effect and a spontaneous AHE switchable by electric polarization. Reversible polarization at one of the interfaces in a three-layer MnBi2Te4 film drives a metal-insulator transition, as well as switching between the AHE and quantum AHE (QAHE). Engineering interlayer polarization in a three-layer MnBi2Te4 film allows converting MnBi2Te4 from a trivial insulator to a Chern insulator.
Article
Chemistry, Multidisciplinary
Fangyang Zhan, Junjie Zeng, Zhuo Chen, Xin Jin, Jing Fan, Tingyong Chen, Rui Wang
Summary: We propose that Floquet engineering can be used to realize the nonequilibrium quantum anomalous Hall effect (QAHE) with tunable Chern number. By irradiating circularly polarized light (CPL), the hybridization of Floquet sidebands in the two-dimensional family MSi2Z4 can lead to the formation of QAHE related to valley polarization (VP-QAHE). The Chern number of VP-QAHE can be highly tunable by adjusting the frequency, intensity, and handedness of CPL, allowing for the exploration of emergent topological phases under light irradiation.
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
Xinming Wu, Runhan Li, Xiaorong Zou, Baibiao Huang, Ying Dai, Chengwang Niu
Summary: In this study, we propose that robust quantum anomalous Hall effect can be achieved in a two-dimensional ferromagnet regardless of the magnetization directions. We identify the intrinsic ferromagnetic material NiBiO3 with nontrivial topology and successfully tune the Chern numbers to obtain a high-Chern-number QAHE.
Article
Multidisciplinary Sciences
Yang Li, Shengnan Xu, Jianfeng Wang, Chong Wang, Baishun Yang, Haiqing Lin, Wenhui Duan, Bing Huang
Summary: The coexistence of the quantum anomalous Hall effect (QAHE) and magnetic skyrmion (SK) can generate a previously unknown SK state called the RK joint topological skyrmion. This state allows tunability of the number and chirality of chiral boundary states (CBS) under external fields, providing additional degrees of freedom for manipulation. Furthermore, external fields can induce a continuous topology phase transition from K-space QAHE to R-space SK, serving as an ideal platform to understand crossover phenomena of multiple-space topologies.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
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)
Article
Multidisciplinary Sciences
Myoung-Woo Yoo, J. Tornos, A. Sander, Ling-Fang Lin, Narayan Mohanta, A. Peralta, D. Sanchez-Manzano, F. Gallego, D. Haskel, J. W. Freeland, D. J. Keavney, Y. Choi, J. Strempfer, X. Wang, M. Cabero, Hari Babu Vasili, Manuel Valvidares, G. Sanchez-Santolino, J. M. Gonzalez-Calbet, A. Rivera, C. Leon, S. Rosenkranz, M. Bibes, A. Barthelemy, A. Anane, Elbio Dagotto, S. Okamoto, S. G. E. te Velthuis, J. Santamaria, Javier E. Villegas
Summary: The anomalous Hall effect (AHE) in ferromagnets can be caused by intrinsic and extrinsic mechanisms. The interplay between correlated physics and topological phenomena at the interface between a ferromagnet La0.7Sr0.3MnO3 and a semimetallic SrIrO3 results in a large AHE with high anomalous Hall conductivity and Hall angle values.
NATURE COMMUNICATIONS
(2021)
Article
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
Yi-Ming Dai, Si-Si Wang, Yan Yu, Ji-Huan Guan, Hui-Hui Wang, Yan-Yang Zhang
Summary: In a quantum Hall effect, current carrying states shrink to a single energy value in the thermodynamic limit, while in a quantum anomalous Hall effect, current carrying states have finite spectrum widths and densities. Other states in the bulk band are localized and may contribute to the formation of a topological Anderson insulator.
Article
Chemistry, Multidisciplinary
Han Tay, Yi-Fan Zhao, Ling-Jie Zhou, Ruoxi Zhang, Zi-Jie Yan, Deyi Zhuo, Moses H. W. Chan, Cui-Zu Chang
Summary: The quantum anomalous Hall (QAH) insulator, which carries dissipation-free chiral edge current, has the potential for energy-efficient transformative information technology. However, practical applications of QAH insulators have been elusive due to their low working temperature and degradation in ambient conditions. In this study, we investigated the degradation of QAH devices stored in different environments and found that the use of a protective layer or an argon glovebox can minimize degradation and preserve the stable QAH properties. Our findings provide a route towards preserving the dissipation-free chiral edge state for potential applications in quantum information technology.
Article
Materials Science, Multidisciplinary
Hairui Bao, Bao Zhao, Jiayong Zhang, Yang Xue, Tong Zhou, Zhongqin Yang
Summary: We investigate the electronic and topological properties of a Mo adsorbed square-octagon Sb monolayer (Mo@so-Sb) using first-principles calculations. Our study reveals how a trivial insulator can be transformed into a bipolar magnetic semiconductor (BMS) and further into a spintronics-favorable half semiconductor (HS) or half metal by strain engineering. With 3.7% compressive strain, we achieve a quantum anomalous Hall (QAH) state in Mo@so-Sb with a high Chern number (C = 4), characterized by the appearance of four gapless chiral edge states within the nontrivial band gap. We demonstrate the control of the interesting BMS, HS, and QAH states using Mo adsorption concentrations.
Article
Chemistry, Multidisciplinary
Peng Zhang, Purnima P. Balakrishnan, Christopher Eckberg, Peng Deng, Tomohiro Nozaki, Su Kong Chong, Patrick Quarterman, Megan E. Holtz, Brian B. Maranville, Gang Qiu, Lei Pan, Eve Emmanouilidou, Ni Ni, Masashi Sahashi, Alexander Grutter, Kang L. Wang
Summary: The exchange-coupled CBST and Al-Cr2O3 interface have perpendicular magnetic moments, leading to an exchange-biased QAH effect. The magnitude and sign of the exchange bias can be effectively controlled using a field training process. This study demonstrates the use of exchange bias to manipulate the QAH state.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
E. Georgopoulou-Kotsaki, P. Pappas, A. Lintzeris, P. Tsipas, S. Fragkos, A. Markou, C. Felser, E. Longo, M. Fanciulli, R. Mantovan, F. Mahfouzi, N. Kioussis, A. Dimoulas
Summary: The 2D van der Waals ferromagnetic metals FexGeTe2 with x = 3-5 have attracted significant attention. In this study, epitaxial Fe5-dGeTe2 (FGT) heterostructures were grown on insulating crystalline substrates using Molecular Beam Epitaxy (MBE). The addition of Bi2Te3 topological insulator (TI) to FGT films significantly enhanced the saturation magnetization and Curie temperature (Tc), with record values of 570 K obtained.
Article
Physics, Multidisciplinary
Daniel S. S. Sanchez, Tyler A. A. Cochran, Ilya Belopolski, Zi-Jia Cheng, Xian P. Yang, Yiyuan Liu, Tao Hou, Xitong Xu, Kaustuv Manna, Chandra Shekhar, Jia-Xin Yin, Horst Borrmann, Alla Chikina, Jonathan D. D. Denlinger, Vladimir N. N. Strocov, Weiwei Xie, Claudia Felser, Shuang Jia, Guoqing Chang, M. Zahid Hasan
Summary: The classification of electronic phases is based on two prominent paradigms: correlations and topology. Electron correlations lead to superconductivity and charge density waves, while the Berry phase gives rise to electronic topology. The combination of these two paradigms has prompted the search for electronic instabilities near the Fermi level of topological materials. This study identifies the electronic topology of chiral fermions as the driving force behind van Hove singularities that host electronic instabilities in the surface band structure.
Article
Physics, Multidisciplinary
Norbert H. H. Freitag, Christopher F. F. Reiche, Volker Neu, Parul Devi, Ulrich Burkhardt, Claudia Felser, Daniel Wolf, Axel Lubk, Bernd Buechner, Thomas Muehl
Summary: This article presents a quantitative magnetic force microscopy technique that can simultaneously map one magnetic stray-field component and its spatial derivative. It is applied to investigate circular magnetic nano-domains in MnNiGa bulk samples, providing bubble diameters and spatial extent in depth. The experimental results indicate that the magnetic bubbles have a significant spatial extent in depth and a buried bubble top base.
COMMUNICATIONS PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Hyeuk Jin Han, Sushant Kumar, Gangtae Jin, Xiaoyang Ji, James L. Hart, David J. Hynek, Quynh P. Sam, Vicky Hasse, Claudia Felser, David G. Cahill, Ravishankar Sundararaman, Judy J. Cha
Summary: The increasing resistance of copper (Cu) interconnects in integrated circuits is a major challenge for downscaling beyond 7 nm technology. Topological semimetals like molybdenum phosphide (MoP) nanowires show unprecedented resistivity scaling, superior to nanoscale Cu interconnects. MoP has better stability against electromigration and resistance to surface oxidation compared to Cu, making it an attractive alternative for the scaling challenge of Cu interconnects.
ADVANCED MATERIALS
(2023)
Article
Multidisciplinary Sciences
Chunyu Guo, A. Alexandradinata, Carsten Putzke, Amelia Estry, Teng Tu, Nitesh Kumar, Feng-Ren Fan, Shengnan Zhang, Quansheng Wu, Oleg V. Yazyev, Kent R. Shirer, Maja D. Bachmann, Hailin Peng, Eric D. Bauer, Filip Ronning, Yan Sun, Chandra Shekhar, Claudia Felser, Philip J. W. Moll
NATURE COMMUNICATIONS
(2023)
Correction
Multidisciplinary Sciences
Yudi Zhang, Kathryn E. Arpino, Qun Yang, Naoki Kikugawa, Dmitry A. Sokolov, Clifford W. Hicks, Jian Liu, Claudia Felser, Guowei Li
NATURE COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Subhajit Roychowdhury, Mengyu Yao, Kartik Samanta, Seokjin Bae, Dong Chen, Sailong Ju, Arjun Raghavan, Nitesh Kumar, Procopios Constantinou, Satya N. Guin, Nicholas Clark Plumb, Marisa Romanelli, Horst Borrmann, Maia G. Vergniory, Vladimir N. Strocov, Vidya Madhavan, Chandra Shekhar, Claudia Felser
Summary: In this study, the electronic structure of ferromagnetic EuCd2As2, predicted to be an ideal Weyl semimetal, is investigated using angle-resolved photoemission spectroscopy and scanning tunneling microscopy. The experimental results are in close agreement with the first principles calculations. Furthermore, anomalous Hall conductivity and Nernst effect are observed, resulting from the non-zero Berry curvature and the topological Hall effect arising from changes in the band structure caused by spin canting produced by magnetic fields. These findings provide insights into exotic quantum phenomena in inorganic topological materials with multiple pairs of Weyl nodes.
Article
Materials Science, Multidisciplinary
Hua Lv, Edouard Lesne, Rebeca Ibarra, Yan Sun, Anastasios Markou, Claudia Felser
Summary: In this study, the structural, magnetic, and electrical magnetotransport properties of 24 and 51 nm thick B20-RhSi thin films grown by magnetron sputtering were investigated. The films exhibited a nonmagnetic ground state and metallic behavior. It was confirmed that the temperature-dependent electrical resistivity is governed by electron-phonon scattering. The ability to grow textured-epitaxial thin films of nonmagnetic B20 chiral topological semimetals is an important step toward designing chiraltronic devices with novel functionalities.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Luca Tomarchio, Sen Mou, Lorenzo Mosesso, Anastasios Markou, Edouard Lesne, Claudia Felser, Stefano Lupi
Summary: In this paper, we investigate the terahertz emission from thin films of the magnetic topological nodal semimetal Co2MnGa when excited by femtosecond optical pulses. We identify multiple THz generation mechanisms, including a photon-drag effect induced by radiation pressure and a photovoltaic effect from the topological surface states of CMG. This interplay between generation mechanisms highlights the potential of Co2MnGa topological nodal semimetals for THz emitter devices.
ACS APPLIED ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Andrew M. Ochs, Gerhard H. Fecher, Bin He, Walter Schnelle, Claudia Felser, Joseph P. Heremans, Joshua E. Goldberger
Summary: KMgBi is a quantum material that exhibits axis-dependent conduction polarity and a greatly enhanced ordinary Nernst effect (ONE). It shows a significant zero-field transverse thermoelectric response and a new type of Nernst effect.
ADVANCED MATERIALS
(2023)
Review
Nanoscience & Nanotechnology
Georgios Varnavides, Amir Yacoby, Claudia Felser, Prineha Narang
Summary: As high-quality single-crystal materials used in electronic devices reach smaller scales, charge-transport phenomena lead to inhomogeneous spatial signatures with significant effects on material properties. These signatures, including spatially varying dissipation and interface resistance, are crucial for device control. This Review examines the inhomogeneous charge flow signatures in conductors, focusing on electron hydrodynamics, where electrons exhibit strong interactions and flow collectively like fluids. Recent experimental advances and theoretical frameworks are discussed, along with new charge-transport phenomena introduced by crystal symmetry in materials.
NATURE REVIEWS MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Irian Sanchez-Ramirez, Maia G. Vergniory, Claudia Felser, Fernando de Juan
Summary: Among the quasi-one-dimensional transition metal tetrachalcogenides (MSe4)nI (M = Nb,Ta), the n = 3 compounds exhibit structural transitions with puzzling transport behavior instead of charge density waves. Recent discovery of a metallic polytype of (TaSe4)3I with coexisting ferromagnetism and superconductivity at low temperature challenges previous reports. In this study, ab initio and tight-binding band-structure calculations are used to explain the observed transport gaps and clarify the controversy regarding ARPES and optical conductivity experiments. The effect of small extrinsic hole doping and its implications for magnetism and superconductivity are also discussed.
Article
Materials Science, Multidisciplinary
Lun-Hui Hu, Chunyu Guo, Yan Sun, Claudia Felser, Luis Elcoro, Philip J. W. Moll, Chao-Xing Liu, Andrei Bernevig
Summary: In this study, a hierarchical structure of quasisymmetries and their corresponding nodal structures in the chiral crystal material CoSi are revealed through two different approaches of perturbation expansions. Quasisymmetries are found to play a crucial role in the physical responses of the system and can protect the existence of nodal planes.
Article
Materials Science, Multidisciplinary
Eleanor F. Scott, Katherine A. Schlaak, Poulomi Chakraborty, Chenguang Fu, Satya N. Guin, Safa Khodabakhsh, Ashley E. Paz Y. Puente, Claudia Felser, Brian Skinner, Sarah J. Watzman
Summary: In this study, it was discovered that polycrystalline NbP exhibits a large Nernst effect and a large magneto-Seebeck effect simultaneously, which is rarely observed in a single material at the same temperature. Through doping, the temperature dependence of these magnetothermoelectric effects can be altered, providing a potential tuning mechanism for device applications.
Article
Engineering, Electrical & Electronic
Ryotaro Okabe, Mingda Li, Yuma Iwasaki, Nicolas Regnault, Claudia Felser, Masafumi Shirai, Alexander Kovacs, Thomas Schrefl, Atsufumi Hirohata
Summary: This letter summarizes the recent development of using artificial intelligence and machine learning in the search for magnetic materials, and briefly introduces the approaches used in materials discovery. The authors also provide a flowchart to assist in selecting the appropriate methods for material search. The letter also covers the authors' recent research activities in magnetism and quantum materials.
IEEE MAGNETICS LETTERS
(2023)