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Time-reversal symmetry breaking Weyl semimetal and tunable quantum anomalous Hall effect in a two-dimensional metal-organic framework

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Physical Review B 2023年第5期108卷 054404-054404页

作者： Xiaoming Zhang Yefeng Li Tingli He Min Zhao Lei Jin Cong Liu Xuefang Dai Ying Liu Hongkuan Yuan Guodong Liu State Key Laboratory of Reliability and Intelligence of Electrical Equipment and School of Materials Science and Engineering Hebei University of Technology Tianjin 300130 China School of Physical Science and Technology Southwest University Chongqing China

Exploring the relationship between magnetism and band topology has become a popular research topic in condensed matter physics. In this work, we investigate this interplay in a two-dimensional (2D) metal-organic framework (MOF) Mn3(C6O6)2. We discover that this MOF has a “soft” ferromagnetic property, making it possible to control the topological phases by adjusting the magnetization direction. In its ground state, the MOF has Weyl points precisely located at the Fermi level and only in one spin channel, which means it can be described as an ideal, fully spin-polarized 2D Weyl semimetal. We determine that the stability of these Weyl points is protected by the vertical mirror symmetries. Particularly, the Weyl point can be preserved even with considering the spin-orbital coupling, with an in-plane magnetization direction parallel to the mirror normal vector. By altering the in-plane magnetization away from the normal vector of the vertical mirror symmetry, we demonstrate that the Weyl point is gapped, transformed into the quantum anomalous Hall (QAH) phase, resulting in a chiral edge state at the boundary. We calculate a Chern number to capture the main feature of the QAH, which indicates quantized Hall conductance. Furthermore, by rotating the magnetization direction in the plane, we discover that the Weyl point is a critical point where the QAH changes the sign of the Chern number, along with inversing the propagating direction of the chiral edge state. Overall, our findings highlight Mn3(C6O6)2 as a promising material candidate for studying the interplay between topology and magnetism, Weyl semimetal, and QAH phases.

关键词： Density of states Edge states Electronic structure Magnetism Quantum phase transitions Spin-orbit coupling Topological materials Weyl semimetal First-principles calculations Symmetries Wannier function methods k dot p method

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Mo-based perpendicularly magnetized thin films with low damping for fast and low-power consumption magnetic memory

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science China(Physics,Mechanics & Astronomy) 2022年第8期65卷 129-139页

作者： Houyi Cheng Boyu Zhang Yong Xu Shiyang Lu Yuxuan Yao Rui Xiao Kaihua Cao Yongshan Liu Zilu Wang Renyou Xu Danrong Xiong Yan Wang Helin Ma Sylvain Eimer Chao Zhao Weisheng Zhao Fert Beijing Institute Ministry of Industry and Information Technology Key Laboratory of SpintronicsSchool of Integrated Circuit Science and EngineeringBeihang UniversityBeijing100191China Hefei Innovation Research Institute Anhui High Reliability Chips Engineering LaboratoryBeihang UniversityHefei230013China Beihang-Geortek Joint Microelectronics Institute Qingdao Research InstituteBeihang UniversityQingdao266000China Beijing Superstring Academy of Memory Technology Beijing100176China

Perpendicular magnetic anisotropy-based magnetic tunnel junctions(p-MTJs) with low Gilbert damping constant(α) are of particular interest for fast and low-power consumption magnetic random-access memory(MRAM). However, obtaining a faster switching speed and lower power consumption is still a big challenge. Herein, we report a Mo-based perpendicular double free layer structure with a low Gilbert damping constant of 0.02 relative to W-based films, as measured by time-resolved magnetooptical Kerr effect equipment. To show the influence of different film structures on the Gilbert damping constant, we measured the Mo-based single free layer. Thereafter, we deposited the full stacks with the Mo-based double free layer and obtained a high tunneling magnetoresistance of 136.3% and high thermal stability. The results of high-resolution transmission electron microscopy(HR-TEM) and energy-dispersive X-ray spectroscopy(EDS) showed that the Mo-based films had better crystallinity,sharper interfaces, and weaker diffusion than the W-based films and thus produced a weaker external contribution of the Gilbert damping constant. As a result of the weak spin-orbit coupling in the Mo-based structure, the intrinsic contribution of the Gilbert damping constant was also weak, thereby leading to the small Gilbert damping constant of the Mo-based stacks. In addition, the macro-spin simulation results demonstrated that the magnetization switching by the spin transfer torque of the Mo-based MTJs was faster than that of the W-based MTJs. These findings help to understand the mechanism behind the good performance of Mo-based p-MTJ films and show the great promise of these structures in low-power consumption MRAM or other spintronic devices.

关键词： CoFeB/MgO Gilbert damping constant perpendicular magnetic anisotropy fast and low-power consumption memory magnetic tunnel junctions

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Oxidized Nb_(2)C MXene as catalysts for lithium-sulfur batteries:Mitigating the shuttle phenomenon by facilitating catalytic conversion of lithium polysulfides

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Journal of Materials science & technology 2022年第24期119卷 45-52页

作者： Cailing Song Wen Zhang Qianwen Jin Yan Zhao Yongguang Zhang Xin Wang Zhumabay Bakenov School of Materials Science and Engineering State Key Laboratory of Reliability and Intelligence of Electrical EquipmentHebei University of TechnologyTianjin 300130China South China Academy of Advanced Optoelectronics&International Academy of Optoelectronics at Zhaoqing South China Normal UniversityGuangzhou 510006China Department of Chemical and Materials Engineering National Laboratory AstanaInstitute of Batteries LLPNazarbayev UniversityNur-Sultan 010000Kazakhstan

Extensive research has been devoted to lithium-sulfur(Li-S)batteries due to their overwhelming promises and advantages such as high theoretical capacity(1675 m Ah g^(-1)),extremely cost effectiveness and abundance and availability of ***,a sluggish electrochemical kinetics of the battery limited by a slow conversion of lithium polysulfide(LiPSs)intermediates and Li PSs shuttle effect severely hinder its development towards industrial ***,we designed the oxidized Nb2_(C)MXene with amorphous carbon(Nb_(2)O_(5)/C)composites as sulfur host using CO_(2)treatment to address the above *** Nb_(2)O_(5)/C composites with high conductivity are directly employed as sulfur hosts for Li-S battery capable to remarkably mitigate the shuttle phenomenon due to a combined effect of their Li PSs trapping ability and catalytic activity towards their accelerated ***,the unique layered structure of the composite facilitates ion transfer and accommodates the volume changes of the cathode during *** this rational design,the resultant Li-S batteries exhibit superior electrochemical performance with a high initial specific capacity of 745 m Ah g^(-1)at 1.0 C and a reversible capacity of 620 m Ah g^(-1)at a high rate cycling at 3.0 C.

关键词： Oxidized Nb_(2)C MXene Li-S batteries Lithium polysulfides conversion Electrochemical performance

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Effect of proton irradiation dose rate and implanted hydrogen ions on spinodal decomposition in thermally aged EQ308L stainless steel weld metal 4

Effect of proton irradiation dose rate and implanted hydroge...

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2023 4th International Conference on Material Chemistry and Composite Materials, MCCM 2023

作者： Li, Yuanfei Peng, Jianchao Yin, Jian Liang, Xue Yang, Xiaofeng Xu, Chaoliang Jia, Wenqing Quan, Qiwei Qian, Wangjie Liu, Xiangbing Liu, Wenqing Material Engineering Technology Center Suzhou Nuclear Power Research Institute Suzhou215004 China Institute of Materials School of Materials Science and Engineering Shanghai University Shanghai200444 China Key Laboratory for Microstructures Shanghai University Shanghai200444 China National Engineering Research Center for Nuclear Power Plant Safety and Reliability Suzhou215004 China

Stainless steel welds with a ferritic phase are extensively utilized in nuclear power plants. Spinodal decomposition stands as the primary factor contributing to the degradation of their service performance. Ion irradiation has been widely employed to investigate the damage behavior of materials. However, varying irradiation parameters, such as dose rate and implanted ions, are believed to result in significant differences in the extent of spinodal decomposition. In this paper, proton irradiation experiments were conducted at different dose rates on thermally aged EQ308L stainless steel welds. Spinodal decomposition within the ferrite at various radiation depths was compared and analyzed by using atom probe tomography to unveil the effects of dose rate and implanted hydrogen ions. The results reveal that, under conditions of high dose rate irradiation, spinodal decomposition can be partially alleviated when compared to the initial thermally aged state. Conversely, under low dose rate irradiation conditions, spinodal decomposition exhibits an enhancement trend. This difference may be attributed to the interplay between irradiation-enhanced diffusion and atomic mixing. Therefore, the dose rate significantly influences the progression of spinodal decomposition. Furthermore, implanted hydrogen ions may also inhibit spinodal decomposition within the ferrite, potentially by promoting the recombination of irradiation defects. © Published under licence by IOP Publishing Ltd.

关键词： Ferrite

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Pt and Te codoped ultrathin MoS_(2) nanosheets for enhanced hydrogen evolution reaction with wide pH range

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Rare Metals 2022年第2期41卷 378-384页

作者： Cui-Hua An Wei Kang Qi-Bo Deng Ning Hu National Engineering Research Center for Technological Innovation Method and Tool School of Mechanical EngineeringHebei University of TechnologyTianjin 300401China Key Laboratory of Advanced Energy Materials Chemistry(MOE) College of ChemistryNankai UniversityTianjin 300071China Institute for New Energy Materials&Low-Carbon Technologies School of Materials Science and EngineeringTianjin University of TechnologyTianjin 300384China State Key Laboratory of Reliability and Intelligence Electrical Equipment Hebei University of TechnologyTianjin 300130China

Transition metal dichalcogenides,especially MoS_(2),have been examined as promising catalysts for hydrogen evolution reaction(HER).Meanwhile,MoS_(2)with various nanostructures and exposed more active sites has been broadly explored for boosting the HER performances at wide pH ***,a synergistic Pt and Te codoping strategy has been used to enhance the catalytic performance(including reducing the overpotential and promoting the HER reaction kinetics)of ultrathin MoS_(2)nanosheets in alkaline and acid electrolytes,which has delivered better than single Pt doping or single Te doping.

关键词： doping kinetics synergistic

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Investigation of Trap States and Reverse Leakage in Fully-Vertical GaN Schottky Barrier Diodes with Laser Lift-Off Substrate

Investigation of Trap States and Reverse Leakage in Fully-Ve...

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International Symposium on Power Semiconductor Devices and Ics (ISPSD)

作者： Feng Zhou Wei Qi Teng Ma Can Zou Junfan Qian Weizong Xu Yiwang Wang Dong Zhou Fangfang Ren Dunjun Chen Rong Zhang Youdou Zheng Hai Lu School of Electronic Science and Engineering Nanjing University Nanjing China The Science and Technology on Reliability Physics and Application of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou China

ISBN: (数字)9798350394825

ISBN: (纸本)9798350394832

Lase lift-off (LLO) substrate technology is a promising solution for realizing fully vertical GaN devices based on foreign substrates. By performing deep-level transient spectroscopy (DLTS) experiments and temperature-dependent leakage current characterizations, this work investigates the trap states and leakage mechanisms of fully-vertical GaN Schottky barrier diodes (SBDs) based on LLO substrate, laser annealing and N-implantation termination. By fitting the DLTS spectral signal, the energy levels of the two electron trap states are determined to be $E_{C}$ - 0.6 e V and $E_{C}$ - 0.21 eV respectively, which should originate from the intrinsic traps in GaN epitaxy rather than being introduced by the LLO process. Furthermore, the leakage currents of the device are found to be dominated by Poole-Frenkel emission (PFE, < 35 V), variable range hopping (VRH, 35 ~ 100 V) and trap-assisted tunneling (TAT, > 100 V), respectively, as the bias voltage increases. These results provide important new insights into the implementation of laser lift-off technology in GaN-based power devices.

关键词： Performance evaluation Schottky diodes Electron traps Spectroscopy Annealing Semiconductor lasers Schottky barriers

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Promoting spintronic terahertz radiation via Tamm plasmon coupling

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Photonics Research 2023年第6期11卷 1057-1066页

作者： YUNQING JIANG HONGQING LI XIAOQIANG ZHANG FAN ZHANG YONG XU YONGGUANG XIAO FENGGUANG LIU ANTING WANG QIWEN ZHAN WEISHENG ZHAO School of Integrated Circuit Science and Engineering Hefei Innovation Research InsitituteBeihang UniversityBeijing 100191China Anhui High Reliability Chips Engineering Laboratory Hefei 230013China School of Materials Science and Engineering Xiangtan UniversityXiangtan 411105China Department of Optics and Optical Engineering University of Science and Technology of ChinaHefei 230026China School of Optical-Electrical and Computer Engineering University of Shanghai for Science and TechnologyShanghai 200093China

Spectral fingerprint and terahertz(THz)field-induced carrier dynamics demands the exploration of broadband and intense THz signal *** THz emitters(STEs),with high stability,a low cost,and an ultrabroad bandwidth,have been a hot topic in the field of THz *** of the main barriers to their practical application is lack of an STE with strong radiation ***,through the combination of optical physics and ultrafast photonics,the Tamm plasmon coupling(TPC)facilitating THz radiation is realized between spin THz thin films and photonic crystal *** results show that the spectral absorptance can be increased from 36.8%to 94.3%for spin THz thin films with *** coupling with narrowband resonance not only improves the optical-to-spin conversion efficiency,but also guarantees THz transmission with a negligible loss(~4%)for the photonic crystal *** to the simulation,we prepared this structure successfully and experimentally realized a 264%THz radiation ***,the spin THz thin films with TPC exhibited invariant absorptivity under different polarization modes of the pump beam and weakening confinement on an obliquely incident pump *** approach is easy to implement and offers possibilities to overcome compatibility issues between the optical structure design and low energy consumption for ultrafast THz optospintronics and other similar devices.

关键词： pump polarization coupling

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Multi-objective Optimization of Repulsive Force Actuator for Vacuum Circuit Breaker 30

Multi-objective Optimization of Repulsive Force Actuator for...

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30th International Symposium on Discharges and Electrical Insulation in Vacuum, ISDEIV 2023

作者： Li, Peiyuan Liu, Xiaoming Chen, Hai Jiang, Wentao Zhou, Yongjie Hebei University of Technology State Key Laboratory of Reliability and Intelligence of Electrical Equipment Tianjin China Tiangong University School of Control Science and Engineering Tianjin China Shanghai Qiteng Electric Co. Ltd. Shanghai China

ISBN: (纸本)9784886864369

The fast DC vacuum switch driven by repulsive force actuator is the key equipment for the control and protection of the new energy power system. Its operating speed directly determines the interruption time of the DC vacuum switch. This paper takes fast 400V DC vacuum switch as the research object, studies the dynamic output characteristics, establishes the finite element numerical analysis model of electromagnetic repulsive force actuator, simulates and analyzes the influence of opening capacitors and charging voltage on the dynamic performance of fast switching. Moreover, the multi-objective artificial jellyfish optimizer is applied to design the repulsive force actuator. Based on the optimized 400V DC vacuum switch, the dynamic output performance of the fast switch has been obtained and analyzed. And the numerical simulation results show that the dynamic motion characteristics and energy conversion efficiency of the fast switch can be improved within 2.0ms. © 2023 IEEJ.

关键词： Electric circuit breakers

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Fault Feature Recognition Of Satellite Power System Based On Incremental Learning

Fault Feature Recognition Of Satellite Power System Based On...

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Prognostics and System Health Management Conference (PHM-Qingdao)

作者： Zhipeng Li YANG Yang Yanchen Dong Baolong Zhu Mingliang Suo School of Reliability and Systems Engineering Beihang University Beijing China No.31850 Unit People's Liberation Army of China Beijing China School of Information and Automation Engineering Qilu University of Technology (Shandong Academy of Sciences) Jinan China National Key Laboratory of Science and Technology on Reliability and Environmental Engineering Institute of Reliability Engineering School of Reliability and Systems Engineering Beihang University Beijing China

ISBN: (数字)9798350354010

ISBN: (纸本)9798350354027

In modern communications and technology, satellite power systems play a central role, and their reliability and fault diagnosis technology are increasingly important. Traditional fault diagnosis methods mainly include signal processing and model-based methods, but they are often inefficient and have limited accuracy when processing complex data sets. This paper proposes a feature selection algorithm based on incremental learning to improve the efficiency and accuracy of fault diagnosis. Its advantage is that it can only evaluate the newly added feature set without the need to reprocess the entire data set, thus optimizing the feature selection process and significantly improving the efficiency and response speed of the algorithm. In order to verify its effectiveness, this article selected 8 public data sets and 4 satellite power system simulation data sets for testing. Then, widely used algorithms are introduced to compare with the algorithm proposed in this article for a more comprehensive comparative analysis. By comparing the differences in running time and classification accuracy of the algorithms, it is concluded that the algorithm proposed in this article can significantly reduce the running time while maintaining or improving the classification effect, verifying the feasibility of the algorithm.

关键词： Fault diagnosis Satellites Accuracy Incremental learning Heuristic algorithms Power system dynamics Signal processing algorithms Feature extraction Classification algorithms Testing

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Rule-Based Modelling Approach for Network Application Availability Assessment Under Dynamic Network Restoration Scheme

SSRN

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SSRN 2023年

作者： Yi, Zhiwei Huang, Ning Yang, Qihang Zheng, Xiangyu School of Reliability and System Engineering Beihang University Beijing100191 China Key Laboratory of Science Technology on Reliability Environmental Engineering Beihang University Beijing100191 China

Under dynamic network restoration scheme of Intelligent Optical Networks (IONs), the application outages are not directly depended on the network node or link failures but affected by the pattern of network failures and the global reallocation of application flow behavior. Existing methodologies on network availability measures target single instances of random failure and evaluating the application availability as the static connection path availability based on topology, which fails to model the dynamic application *** order to capture the application resilience behavior and provide a more effective measurement, this paper proposes a rule-based modelling approach which exploits the general graph algorithm and resource match function as local rules to determine the application contention outcomes of interaction during the restoration procedure. Then application availability is evaluated by means of simulations in terms of recovery time during the system state transition controlled by the rules. © 2023, The Authors. All rights reserved.

关键词： Topology

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