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Experimental observation of multiple topological nodal structure in LaSb_(2)

Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 138-145页

作者： Yuxi Qiao Fuyi wang huaiqiang wang Zicheng Tao Zhicheng Jiang Zhengtai Liu Soohyun Cho Fayuan Zhang Qingkai Meng Wei Xia Yichen Yang Zhe Huang Jishan Liu Zhonghao Liu Zengwei Zhu Shan Qiao Yanfeng Guo Haijun Zhang Dawei Shen State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information TechnologyChinese Academy of SciencesShanghai 200050China National Synchrotron Radiation Laboratory and School of Nuclear Science and TechnologyUniversity of Science and Technology of ChinaHefei 230026China National Laboratory of Solid State Microstructures School of PhysicsNanjing UniversityNanjing 210093China School of Physics and Technology Nanjing Normal UniversityNanjing 210023China School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Wuhan National High Magnetic Field Center and School of Physics Huazhong University of Science and TechnologyWuhan 430074China ShanghaiTech Laboratory for Topological Physics ShanghaiTech UniversityShanghai 201210China Institute of High-Pressure Physics School of Physical Science and Technology Ningbo UniversityNingbo 315211China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Unconventional fermions in the immensely studied topological semimetals are the source for rich exotic topological ***,using symmetry analysis and first-principles calculations,we propose the coexistence of multiple topological nodal structure in LaSb_(2),including topological nodal surfaces,nodal lines and in particular eightfold degenerate nodal points,which have been scarcely observed in a single ***,utilizing angle-resolved photoemission spectroscopy,we confirm the existence of nodal surfaces and eightfold degenerate nodal points in LaSb_(2).The intriguing multiple topological nodal structure might play a crucial role in giving rise to the large linear *** work renews the insights into the exotic topological phenomena in LaSb_(2).

关键词： eightfold degenerate points multiple topological nodal structure angle-resolved photoemission spectroscopy linear unsaturated magnetoresistance

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Three-Dirac-fermion approach to unexpected universal gapless surface states in van der Waals magnetic topological insulators

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中国科学:物理学、力学、天文学英文版 2023年第9期66卷 79-85页

作者： Dinghui wang huaiqiang wang Dingyu Xing Haijun Zhang National Laboratory of Solid State Microstructures School of PhysicsNanjing UniversityNanjing 210093China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

Layered van der Waals(vdW) topological materials, especially the recently discovered MnBi_(2)Te_(4)-family magnetic topological insulators(TIs), have aroused great attention. However, there has been a serious debate about whether the surface states are gapped or gapless for antiferromagnetic(AFM) TI MnBi_(2)Te_(4), which is crucial to the prospect of various magnetic topological phenomena. Here, a minimal three-Dirac-fermion approach is developed to generally describe topological surface states of nonmagnetic/magnetic vdW TIs under the modulation of the interlayer vdW gap. In particular, this approach is applied to address the controversial issues concerning the surface states of vdW AFM TIs. Remarkably, topologically protected gapless Dirac-cone surface states are found to arise due to a small expansion of the interlayer vdW gap on the surface, when the Chern number equals zero for the surface ferromagnetic layer;while the surface states remain gapped in all other cases. These results are further confirmed by our first-principles calculations on AFM TI MnBi_(2)Te_(4). The theorectically discovered gapless Dirac-cone states provide a unique mechanism for understanding the puzzle of the experimentally observed gapless surface states in MnBi_(2)Te_(4).This work also provides a promising way for experiments to realize the intrinsic magnetic quantum anomalous Hall efect in MnBi_(2)Te_(4) films with a large energy gap.

关键词： magnetic topological insulator van der Waals gap Dirac-fermion model gapless surface state

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Tunable dynamical magnetoelectric effect in antiferromagnetic topological insulator MnBi_(2)Te_(4) films

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npj Computational Materials 2021年第1期7卷 1101-1106页

作者： Tongshuai Zhu huaiqiang wang Haijun Zhang Dingyu Xing National Laboratory of Solid State Microstructures School of PhysicsNanjing UniversityNanjingChina Department of Physics University of ZurichZurichSwitzerland Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjingChina

Axion was postulated as an elementary particle to solve the strong charge conjugation and parity puzzle,and later axion was also considered to be a possible component of dark matter in the ***,the existence of axions in nature has not been ***,axions arise out of pseudoscalar fields derived from the Chern–Simons theory in condensed matter *** antiferromagnetic insulators,the axion field can become dynamical due to spin-wave excitations and exhibits rich exotic phenomena,such as axion ***,antiferromagnetic dynamical axion insulator has yet been experimentally identified in realistic *** recently,MnBi_(2)Te_(4)was discovered to be an antiferromagnetic topological insulator with a quantized static axion field protected by inversion symmetry P and magnetic-crystalline symmetry ***,we studied MnBi_(2)Te_(4)films in which both the P and S symmetries are spontaneously broken and found that substantially enhanced dynamical magnetoelectric effects could be realized through tuning the thickness of MnBi_(2)Te_(4)films,temperature,or element *** results show that thin films of MnBi_(2)Te_(4)and related compounds could provide a promising material platform to experimentally study axion electrodynamics.

关键词： materials dynamical insulator

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Nonlinear Hall Effect in Antiferromagnetic Half-Heusler Materials

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Chinese Physics Letters 2021年第5期38卷 78-83页

作者： Cheng Chen huaiqiang wang Zhilong Yang Haijun Zhang National Laboratory of Solid State Microstructures School of PhysicsNanjing UniversityNanjing 210093China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

It has recently been demonstrated that various topological states, including Dirac, Weyl, nodal-line, and triplepoint semimetal phases, can emerge in antiferromagnetic(AFM) half-Heusler compounds. However, how to determine the AFM structure and to distinguish different topological phases from transport behaviors remains unknown. We show that, due to the presence of combined time-reversal and fractional translation symmetry, the recently proposed second-order nonlinear Hall effect can be used to characterize different topological phases with various AFM configurations. Guided by the symmetry analysis, we obtain expressions of the Berry curvature dipole for different AFM configurations. Based on the effective model, we explicitly calculate the Berry curvature dipole, which is found to be vanishingly small for the triple-point semimetal phase, and large in the Weyl semimetal phase. Our results not only put forward an effective method for the identification of magnetic orders and topological phases in AFM half-Heusler materials, but also suggest these materials as a versatile platform for engineering the nonlinear Hall effect.

关键词： AFM Dirac Hamiltonian Nonlinear Hall Effect in Antiferromagnetic Half-Heusler Materials

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Composite topological nodal lines penetrating the Brillouin zone in orthorhombic AgF_(2)

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npj Computational Materials 2019年第1期5卷 694-701页

作者： Dexi Shao huaiqiang wang Tong Chen Pengchao Lu Qinyan Gu Li Sheng Dingyu Xing Jian Sun National Laboratory of Solid State Microstructures and Department of Physics Nanjing University210093 NanjingChina Collaborative Innovation Center of Advanced Microstructures 210093 NanjingChina

It has recently been found that nonsymmorphic symmetries can bring many exotic band ***,based on symmetry analysis,we predict that materials with time-reversal symmetry in the space group of Pbca(No.61)possess rich symmetry-enforced band crossings,including nodal surfaces,fourfold degenerate nodal lines and hourglass Dirac loops,which appear in triplets as ensured by the cyclic permutation *** take Pbca AgF_(2) as an example in real systems and studied its band structures with ab initio ***,in the absence of spin-orbit coupling(SOC),besides the above-mentioned band degeneracies,this system features a nodal chain and a nodal armillary sphere penetrating the Brillouin zone(BZ).While with SOC,we find a new configuration of the hourglass Dirac loop/chain with the feature traversing the BZ,which originates from the splitting of a Dirac loop confined in the ***,guided by the bulk-surface correspondence,we calculated the surface states to explore these bulk nodal *** evolution of these interesting nodal phenomena traversing the BZ under two specific uniaxial strains is also discussed.

关键词： nodal symmetry Brillouin

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Floquet spectrum and optical behaviors in dynamic Su–Schrieffer–Heeger modeled waveguide array

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Chinese Optics Letters 2021年第4期19卷 71-76页

作者： Ye Yu Yiwen Song Tao Chen huaiqiang wang Songlin Zhuang Qingqing Cheng School of Optical-Electrical and Computer Engineering University of Shanghai for Science and TechnologyShanghai 200093China National Laboratory of Solid State Microstructures School of PhysicsNanjing UniversityNanjing 210093China

Floquet topological insulators(FTIs) have been used to study the topological features of a dynamic quantum system within the band structure. However, it is difficult to directly observe the dynamic modulation of band structures in FTIs. Here, we implement the dynamic Su–Schrieffer–Heeger model in periodically curved waveguides to explore new behaviors in FTIs using light field evolutions. Changing the driving frequency produces near-field evolutions of light in the high-frequency curved waveguide array that are equivalent to the behaviors in straight arrays. Furthermore, at modest driving frequencies,the field evolutions in the system show boundary propagation, which are related to topological edge modes. Finally, we believe curved waveguides enable profound possibilities for the further development of Floquet engineering in periodically driven systems, which ranges from condensed matter physics to photonics.

关键词： topological photonics insulator waveguide array Floquet

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Delving into the dissimilarities in electrochemical performance and underlying mechanisms for sodium and potassium ion storage in N-doped carbon-encapsulated metallic Cu_(2)Se nanocubes

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Journal of Energy Chemistry 2024年第8期95卷 336-347,I0008页

作者： Xinyu wang Yanan Xu Xiaofeng Liu Lei Tan huaiqiang Gu Xin Du Dan Li College of Chemistry Zhengzhou UniversityZhengzhou 450001HenanChina Green Catalysis Center College of ChemistryZhengzhou UniversityZhengzhou 450001HenanChina Institute of Theoretical Physics Lanzhou UniversityLanzhou 730000GansuChina School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000GansuChina Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education) College of ChemistryNankai UniversityTianjin 300071China State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources College of ChemistryXinjiang UniversityUrumqi 830046XinjiangChina

The large volumetric variations experienced by metal selenides within conversion reaction result in inferior rate capability and cycling stability,ultimately hindering the achievement of superior electrochemical ***,metallic Cu_(2)Se encapsulated with N-doped carbon(Cu_(2)Se@NC)was prepared using Cu_(2)O nanocubes as templates through a combination of dopamine polymerization and hightemperature *** unique nanocubic structure and uniform N-doped carbon coating could shorten the ion transport distance,accelerate electron/charge diffusion,and suppress volume variation,ultimately ensuring Cu_(2)Se@NC with excellent electrochemical performance in sodium ion batteries(SIBs)and potassium ion batteries(PIBs).The composite exhibited excellent rate performance(187.7 mA h g^(-1)at 50 A g^(-1)in SIBs and 179.4 mA h g^(-1)at 5 A g^(-1)in PIBs)and cyclic stability(246,8 mA h g^(-1)at 10 A g^(-1)in SIBs over 2500 cycles).The reaction mechanism of intercalation combined with conversion in both SIBs and PIBs was disclosed by in situ X-ray diffraction(XRD)and ex situ transmission electron microscope(TEM).In particular,the final products in PIBs of K_(2)Se and K_(2)Se_(3)species were determined after discharging,which is different from that in SIBs with the final species of Na_(2)*** density functional theory calculation showed that carbon induces strong coupling and charge interactions with Cu_(2)Se,leading to the introduction of built-in electric field on heterojunction to improve electron ***,the theoretical calculations discovered that the underlying cause for the relatively superior rate capability in SIBs to that in PIBs is the agile Na~+diffusion with low energy barrier and moderate adsorption *** findings offer theoretical support for in-depth understanding of the performance differences of Cu-based materials in different ion storage systems.

关键词： Cu_(2)Se nanocubes DFT calculations Ion storage mechanism Potassium ion batteries Sodium ion batteries

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走向民族区域自治--1921-1949年中国共产党民族政策变迁历史新探

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广西民族研究 2011年第1期 33-40页

作者：王怀强南京大学政府管理学院政治学专业博士研究生南京210093

对1921-1949年中国共产党民族政策变迁历史的全面考察是客观认识与评价当代中国民族区域自治政策之现实合理性与未来发展可能性的知识基础。作为中共新民主主义革命总纲领的一部分,中共的民族政策始终随着新民主主义革命的发展逻辑而不... 详细信息

对1921-1949年中国共产党民族政策变迁历史的全面考察是客观认识与评价当代中国民族区域自治政策之现实合理性与未来发展可能性的知识基础。作为中共新民主主义革命总纲领的一部分,中共的民族政策始终随着新民主主义革命的发展逻辑而不断被重新定义,期间经历了一个逐步成熟、从初期的机械模仿苏联到逐渐立足国情,将马克思列宁主义的民族理论与中国革命的具体实际相结合、最终提出和确立民族区域自治的漫长历史过程。

关键词：民族政策民族自决民族区域自治

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论脱贫攻坚对乡村治理体系和治理能力现代化的战略推进

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云南民族大学学报（哲学社会科学版） 2020年第4期37卷 86-91页

作者：王怀强中共甘肃省委党校/甘肃行政学院甘肃兰州730070

对贫困农村来说,物质上的贫困与治理上的困境往往相伴而生、互为因果。物质贫困与治理困境在贫困农村的共生逻辑,决定了脱贫攻坚战必须既要有效解决物质贫困,也要有效解决治理困境。实践证明,脱贫攻坚战在取得消除农村绝对贫困历史性胜... 详细信息

对贫困农村来说,物质上的贫困与治理上的困境往往相伴而生、互为因果。物质贫困与治理困境在贫困农村的共生逻辑,决定了脱贫攻坚战必须既要有效解决物质贫困,也要有效解决治理困境。实践证明,脱贫攻坚战在取得消除农村绝对贫困历史性胜利的同时,推动乡村治理领域发生了治理权威重塑、治理主体培育、治理资源集聚、治理基础拓展、治理方式变革等重大进步,有力提升了乡村治理体系和治理能力现代化水平,为实施乡村振兴战略提供了有效的治理保障。

关键词：脱贫攻坚乡村治理现代化善治

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急性脑梗死患者卒中后肺炎与预后的关系

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中华医学杂志 2016年第35期96卷 2796-2801页

作者：李慎军胡怀强王晓玲曹秉振济南军区总医院神经内科济南250031

目的探讨急性脑梗死患者卒中后肺炎与预后的关系。方法前瞻性收集2010年8月至2014年8月于济南军区总医院神经内科住院的急性脑梗死患者，记录其年龄、性别、血清肌酐、空腹血糖、美国国立卫生研究院卒中量表（NIHSS）评分、牛津郡社区... 详细信息

目的探讨急性脑梗死患者卒中后肺炎与预后的关系。方法前瞻性收集2010年8月至2014年8月于济南军区总医院神经内科住院的急性脑梗死患者，记录其年龄、性别、血清肌酐、空腹血糖、美国国立卫生研究院卒中量表（NIHSS）评分、牛津郡社区卒中计划分型等基线资料。按照美国疾病控制中心的医院获得性肺炎的标准进行诊断卒中后肺炎。在发病后180d通过电话进行随访，采用改良Rankin量表（mRS）评分对患者的预后进行评价（mRS评分≤2分为预后良好，mRS评分〉2分为预后不良）。采用多元回归分析、卡普兰一迈耶曲线分析卒中后肺炎对预后的影响。结果共纳入1249例急性脑梗死患者。其中，失访173例。有卒中后肺炎组159例，无卒中后肺炎组1090例。与无卒中后肺炎组相比，有卒中后肺炎组年龄大[（67±13）岁比（63±12）岁，P=0．000]，梗死程度重[15（14）比4（4），P=0．000]；患心力衰竭（12．58％比3．40％，P=0．000）、心房纤颤（26．42％比8．81％，P=0．000）、心肌梗死（10．06％比5．05％，P=0．016）、复发性脑梗死（30．19％比22．66％，P=0．045）、牛津郡社区卒中计划分型完全前循环型（46．54％比19．63％，P=0．000）、牛津郡社区卒中计划分型后循环型（39．62％比25．51％，P=0．001）比例高；发病时有意识障碍（60．38％比9．27％，P=0．000）、吞咽困难（34．59％比19．89％，P=0．000）、呕吐（26．42％比8．81％，P=0．000）、失语（35．85％比16．61％，P=0．000）的比例高。预后不良组卒中后肺炎的患病率[29．37％（111／378）]显著高于无卒中后肺炎组[3．73％（26／698）]（P=0．000）。卒中后肺炎是急性脑梗死患者发病后180d内预后不良（OR=2．414，95％CI：1．336～4．361，P=0．004）、病死率高（OR=2．132，95％CI：1．229—3．699，P=0．007）的独立预测因子。合并卒中后肺炎的急性脑梗死患者发病后180d的生存曲线和生存率低于未合并卒中后肺炎的急性脑梗死患者[62．04％（85／137）与93．29％（876／939）；时序检验：x^2=137．32，P=0．000]。结论合并卒中后肺炎的急性脑梗死患者年龄大，梗死程度重；患心力衰竭、心房纤颤、心肌梗死的比例高；发病时有意识障碍的比例高。卒中后肺炎是急性脑梗死患者发病后180d内病死率、预后不良的独立预测因子。

关键词：卒中后肺炎脑梗死预后

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