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Selective flattening of magnon bands in kagome-lattice ferromagnets with Dzyaloshinskii-Moriya interaction

Science China(Physics,Mechanics & Astronomy) 2020年第10期63卷 98-104页

作者： YuHeng Xing FuSheng Ma lifa zhang ZhenYu zhang NNU-SULI Thermal Energy Research Center(NSTER)Center for Quantum Transport and Thermal Energy Science(CQTES) School of Physics and TechnologyNanjing Normal UniversityNanjing 210023China International Center for Quantum Design of Functional Materials(ICQD) Hefei National Laboratory for Physical Sciences at Microscaleand Synergetic Innovation Center of Quantum Information and Quantum PhysicsUniversity of Science and Technology of ChinaHefei 230026China

There is growing interest in revealing exotic properties of collective spin excitations in kagome-lattice ferromagnets such as magnon Hall effects,topological magnon insulators,and flat magnon *** the well-established nearest-neighbor Heisenberg ferromagnet model with Dzyaloshinskii-Moriya interaction(DMI),in this study we uncover intriguing new aspects in the selectivity and topology of flat magnon *** the three magnon bands(except for the top one,which is flat in the absence of DMI),we observe that each of the three bands can be selectively flattened at the critical DMI of D=±√3 J/3 and D=±√3 *** a general DMI,the magnon bands become non-flat;however,there are nested lines that create a David star pattern for all three magnon bands whose flatness is robust during changing exchange coupling or *** to prevailing belief,we show that each of the three flat bands is actually topologically trivial at critical ***,we show that while the middle band remains topologically trivial,for the other two bands,D=0 corresponds to the topological phase transition where their Chern numbers get interchanged;when D=±√3 J,the system undergoes a phase transition to the nonferromagnetic *** central findings increase our understanding of spin excitations for future magnonics applications.

关键词： flat magnon bands kagome lattice ferromagnet Dzyaloshinskii-Moriya interaction

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Bidirectional and Unidirectional Negative Differential Thermal Resistance Effect in a Modified Lorentz Gas Model

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Chinese Physics Letters 2021年第1期38卷 58-62页

作者： Yu Yang XiuLing Li lifa zhang NNU-SULI Thermal Energy Research Center(NSTER)and Center for Quantum Transport and Thermal Energy Science(CQTES) School of Physics and TechnologyNanjing Normal UniversityNanjing 210023China

Recently,the negative differential thermal resistance effect was discovered in a homojunction made of a negative thermal expansion material,which is very promising for realizing macroscopic thermal *** to the Monte Carlo phonon simulation to deal with grain boundaries,we introduce positive temperature-dependent interface thermal resistance in the modified Lorentz gas model and find negative differential thermal resistance *** the homojunction,we reproduce a pair of equivalent negative differential thermal resistance effects in different temperature gradient *** the heterojunction,we realize the unidirectional negative differential thermal resistance effect,and it is accompanied by the super thermal rectification *** this new way to achieve high-performance thermal devices is a new direction,and will provide extensive reference and guidance for designing thermal devices.

关键词： resistance thermal Lorentz

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Tuning thermal transport via phonon localization in nanostructures

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Chinese Physics B 2020年第12期29卷 33-43页

作者： Dengke Ma Xiuling Li lifa zhang NNU-SULI Thermal Energy Research Center(NSTER)and Center for Quantum Transport and Thermal Energy Science(CQTES) School of Physics and TechnologyNanjing Normal UniversityNanjing 210023China

Localization,one of the basic phenomena for wave transport,has been demonstrated to be an effective strategy to manipulate electronic,photonic,and acoustic properties of *** to the wave nature of phonons,the tuning of thermal properties through phonon localization would also be expected,which is beneficial to many applications such as thermoelectrics,electronics,and *** the development of nanotechnology,nanostructures with characteristic length about ten nanometers can give rise to phonon localization,which has attracted considerable attention in recent *** review aims to summarize recent advances with theoretical,simulative,and experimental studies toward understanding,prediction,and utilization of phonon localization in disordered nanostructures,focuses on the effect of phonon localization on thermal *** on previous researches,perspectives regarding further researches to clarify this hecticinvestigated and immature topic and its exact effect on thermal transport are given.

关键词： thermal conductivity phonon localization nanostructure

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The nonlocal transport and switch effect in light-and electric-controlled silicene–superconductor hybrid structure

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Chinese Physics B 2018年第12期27卷 121-126页

作者： Fenghua Qi Jun Cao Jie Cao lifa zhang Center for Quantum Transport and Thermal Energy Science School of Physics and TechnologyNanjing Normal UniversityNanjing 210023China School of Electronic Engineering Nanjing Xiaozhuang UniversityNanjing 211171China College of Science Hohai UniversityNanjing 210098China

We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal *** to the tunable band structure of silicene,a pure crossed Andreev reflection process can be realized under the optical and electrical ***,a switch effect among the exclusive crossed Andreev reflection,the exclusive elastic cotunneling and the exclusive Andreev reflection,where the former two are the nonlocal transports and the third one is the local transport,can be obtained in our system by the modulation of the electric and light *** addition,the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.

关键词： switch effect silicene crossed Andreev reflection

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Chiral phonon activated spin Seebeck effect in chiral materials

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Science China(Physics,Mechanics & Astronomy) 2024年第3期67卷 149-155页

作者： Xiao Li Jinxin Zhong Jinluo Cheng Hao Chen Huiqian Wang Jun Liu Dali Sun lifa zhang Jun Zhou Phonon Engineering Research Center of Jiangsu Province Center for Quantum Transport and Thermal Energy ScienceSchool of Physics and TechnologyNanjing Normal UniversityNanjing 210023China Center for Phononics and Thermal Energy Science China-EU Joint Lab for NanophononicsSchool of Physics Science and EngineeringTongji UniversityShanghai 200092China Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of ScienceChangchun 130033China Department of Mechanical and Aerospace Engineering North Carolina State UniversityRaleigh NC 27606USA Department of Physics North Carolina State UniversityRaleigh NC 27695USA Organic and Carbon Electronics Laboratories(ORaCEL) North Carolina State UniversityRaleigh NC 27606USA

Efficient generation of spin polarization is very important for spintronics and quantum computation. In chiral materials without magnetic order nor spin-orbit coupling, we find a new spin selectivity effect—chiral phonon activated spin Seebeck(CPASS)effect. Starting with the nonequilibrium distribution of chiral phonons under a temperature gradient, the CPASS coefficients are computed based on the Boltzmann transport theory. With both the phonon-drag and band transport contributions, the spin accumulations generated by the CPASS effect exhibit quadratic dependence on the temperature gradient. The strength of the CPASS effect and the relative magnitude of both contributions are tunable by the chemical potential modulation. The CPASS effect, which gives a promising explanation on the traditional chiral-induced spin selectivity effect, provides opportunities for the exploration of advanced spintronic devices based on chiral materials even in the absence of any magnetic order and spin-orbit coupling.

关键词： spin Seebeck effect chiral phonon phonon-drag contribution efficient spin generation

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Introduction of Asymmetry to Enhance Thermal Transport in Porous Metamaterials at Low Temperature

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Chinese Physics Letters 2023年第12期40卷 62-67页

作者：杨宇马登科张力发 Phonon Engineering Research Center of Jiangsu Province Center for Quantum Transport and Thermal Energy ScienceInstitute of Physics Frontiers and Interdisciplinary SciencesSchool of Physics and TechnologyNanjing Normal UniversityNanjing 210023China

Introducing porosity with different degrees of disorder has been widely used to regulate thermal properties of materials, which generally results in decrease of thermal conductivity. We investigate the thermal conductivity of porous metamaterials in the ballistic transport region by using the Lorentz gas model. It is found that the introduction of asymmetry and Gaussian disorder into porous metamaterials can lead to a strong enhancement of thermal conductivity. By dividing the transport process into ballistic transport, non-ballistic transport, and unsuccessful transport processes, we find that the enhancement of thermal conductivity originates from the significant increase ballistic transport ratio. The findings enhance the understanding of ballistic thermal transport in porous materials and may facilitate designs of high-performance porous thermal metamaterials.

关键词： porous transport conductivity

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A thermal conductivity switch via the reversible 2H–1T′phase transition in monolayer MoTe_(2)

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Chinese Physics B 2023年第5期32卷 1-6页

作者：张定波任卫君王珂陈帅张力发倪宇翔张刚 School of Physical Science and Technology Southwest Jiaotong UniversityChengdu 610031China Institute of High Performance Computing A*STAR 138632Singapore Center for Phononics and Thermal Energy Science China-EU Joint Laboratory for NanophononicsSchool of Physics Science and EngineeringTongji UniversityShanghai 200092China School of Automation Xi’an University of Posts and TelecommunicationsShaanxi 710121China NNU-SULI Thermal Energy Research Center and Center for Quantum Transport and Thermal Energy Science(CQTES)School of Physics and TechnologyNanjing Normal UniversityNanjing 210023China

The two-dimensional(2D)material-based thermal switch is attracting attention due to its novel applications,such as energy conversion and thermal management,in nanoscale *** this paper,we observed that the reversible 2H–1T′phase transition in MoTe_(2)is associated with about a fourfold/tenfold change in thermal conductivity along the X/Y direction by using first-principles *** phenomenon can be profoundly understood by comparing the Mo–Te bonding strength between the two *** 2H-MoTe_(2)has one stronger bonding type,while 1T′-MoTe_(2)has three weaker types of bonds,suggesting bonding inhomogeneity in 1T′-MoTe_(2).Meanwhile,the bonding inhomogeneity can induce more scattering of vibration *** weaker bonding indicates a softer structure,resulting in lower phonon group velocity,a shorter phonon relaxation lifetime and larger Gr¨uneisen *** impact caused by the 2H to 1T′phase transition in MoTe_(2)hinders the propagation of phonons,thereby reducing thermal *** study describes the possibility for the provision of the MoTe_(2)-based controllable and reversible thermal switch device.

关键词： thermal switch MoTe_(2) phase transition thermal conductivity mechanism

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探究创造性思维训练如何与小学生体育教学相融合

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当代家庭教育 2020年第31期 148-149页

作者：张立发甘肃省华亭市山寨回族乡教育管理委员会

随着社会经济的发展以及新课程改革的不断深入,小学体育教学的教学目标发生了极大的转变,教师在对学生进行体育知识、体育技能传授的同时,还应对学生进行健康身心状态、健全人格以及创造性思维的培养。因此,这就需要教师应在小学体育教... 详细信息

随着社会经济的发展以及新课程改革的不断深入,小学体育教学的教学目标发生了极大的转变,教师在对学生进行体育知识、体育技能传授的同时,还应对学生进行健康身心状态、健全人格以及创造性思维的培养。因此,这就需要教师应在小学体育教学中通过多元化创造性思维训练的开展,来对学生进行思维能力、创新能力的有效培养,实现学生综合素质能力的全面发展。

关键词：小学体育创造性思维融合策略

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武术与体育比较研究

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湖北体育科技 2008年第6期27卷 645-646页

作者：张立发王维华中师范大学湖北武汉430079

在对武术与体育的最新概念认识的基础上,对中国武术与西方体育的本质、行为规范、修炼或锻炼的侧重点、运动形式等方面进行比较分析,指出中国武术与西方体育之间存在较大差距,即使武术中有体育成分的影子,但最终还是回归于武术范畴。

关键词：武术体育比较

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钢桥疲劳裂纹几何特征对涡流检测信号影响规律研究

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仪表技术与传感器 2024年第1期 94-99页

作者：张立发袁周致远吉伯海庞根河海大学土木与交通学院

针对常规钢桥面板疲劳裂纹检测手段只能贴合表面进行检测的问题,引入涡流检测方法,实现对钢桥面板表面疲劳裂纹的检测。搭建了涡流检测实验平台,设计研发了涡流检测探头,对不同尺寸疲劳裂纹进行横向扫查,研究了不同长度、宽度和深度特... 详细信息

针对常规钢桥面板疲劳裂纹检测手段只能贴合表面进行检测的问题,引入涡流检测方法,实现对钢桥面板表面疲劳裂纹的检测。搭建了涡流检测实验平台,设计研发了涡流检测探头,对不同尺寸疲劳裂纹进行横向扫查,研究了不同长度、宽度和深度特征的疲劳裂纹对检测信号的影响规律。并建立有限元仿真模型,模拟疲劳裂纹扫查过程,验证了钢桥面板疲劳裂纹涡流检测方法的可靠性,为后续疲劳裂纹尺寸精准测量提供依据。实验结果显示:设计的空心圆柱形检测探头能够实现最小尺寸为长度60 mm、宽度0.2 mm、深度5 mm的表面裂纹缺陷的定位检测;检测信号的幅度变化值与裂纹长度、宽度、深度在一定范围内均成正相关,裂纹长度和深度对检测信号影响较大,裂纹宽度对检测信号影响较小。

关键词：涡流检测钢桥疲劳裂纹几何特征检测信号

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