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Chinese physics Letters 2024年第4期41卷 132-138页

作者：朱蒙董建艇李新录郑凡星周晔吴琨张佳 School of physics and wuhan national high magnetic field center Huazhong University of Science and TechnologyWuhan 430074China

In comparison to ferromagnets,antiferromagnets are believed to have superior advantages for applications in next-generation magnetic storage devices,including fast spin dynamics,vanishing stray fields and robust against external magnetic field,etc.However,unlike ferromagnetic orders,which could be detected through tunneling magnetoresistance effect in magnetic tunnel junctions,the antiferromagnetic order(i.e.,Néel vector)cannot be effectively detected by the similar mechanism due to the spin degeneracy of conventional antiferromagnets.Recently discovered spin-splitting noncollinear antiferromagnets,such as Mn_(3)Pt with momentum-dependent spin polarization due to their special magnetic space group,make it possible to achieve remarkable tunneling magnetoresistance effects in noncollinear antiferromagnetic tunnel junctions.Through first-principles calculations,we demonstrate that the tunneling magnetoresistance ratio can reach more than 800% in Mn_(3)Pt/perovskite oxides/Mn_(3)Pt antiferromagnetic tunnel junctions.We also reveal the switching dynamics of Mn_(3)Pt thin film under magnetic fields using atomistic spin dynamic simulation.Our study provides a reliable method for detecting Néel vector of noncollinear antiferromagnets through the tunnel magnetoresistance effect and may pave its way for potential applications in antiferromagnetic memory devices.

关键词： tunneling magnetoresistance momentum

Unconventional room-temperature negative magnetoresistance effect in Au/n-Ge:Sb/Au devices

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Chinese physics B 2024年第3期33卷 602-608页

作者：何雄杨凡黎牛浩峪王立峰易立志许云丽刘敏潘礼庆夏正才 Hubei Engineering Research center of Weak magnetic-field Detection College of ScienceChina Three Gorges UniversityYichang 443002China wuhan national high magnetic field center Huazhong University of Science and TechnologyWuhan 430074China

Non-magnetic semiconductor materials and their devices have attracted wide attention since they are usually prone to exhibit large positive magnetoresistance(MR)effect in a low static magnetic field environment at room temperature.However,how to obtain a large room-temperature negative MR effect in them remains to be studied.In this paper,by designing an Au/n-Ge:Sb/Au device with metal electrodes located on identical side,we observe an obvious room-temperature negative MR effect in a specific 50 T pulsed high magnetic field direction environment,but not in a static low magnetic field environment.Through the analysis of the experimental measurement of the Hall effect results and bipolar transport theory,we propose that this unconventional negative MR effect is mainly related to the charge accumulation on the surface of the device under the modulation of the stronger Lorentz force provided by the pulsed high magnetic field.This theoretical analytical model is further confirmed by regulating the geometry size of the device.Our work sheds light on the development of novel magnetic sensing,magnetic logic and other devices based on non-magnetic semiconductors operating in pulsed high magnetic field environment.

关键词： magnetoresistance germanium-based devices pulsed high magnetic fields

On the evolution and formation of discharge morphology in pulsed dielectric barrier discharge

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Plasma Science and Technology 2024年第4期26卷 101-113页

作者：陈星宇李孟琦王威逸张权治彭涛熊紫兰 State Key Laboratory of Advanced Electromagnetic Technology Huazhong University of Science and TechnologyWuhan 430074People’s Republic of China School of physics Dalian University of TechnologyDalian 116024People’s Republic of China wuhan national high magnetic field center Huazhong University of Science and TechnologyWuhan 430074People’s Republic of China

The discharge morphology of pulsed dielectric barrier discharge(PDBD) plays important roles in its applications. Here, we systematically investigated the effects of the voltage amplitude,discharge gap, and O_(2)content on the PDBD morphology, and revealed the possible underlying mechanism of the U-shaped formation. First, the morphological evolution under different conditions was recorded. A unique U-shaped region appears in the middle edge region when the gap is larger than 2 mm, while the entire discharge region remains columnar under a 2 mm gap in He PDBD. The width of the discharge and the U-shaped region increase with the increase in voltage, and decrease with the increase of the gap and O_(2)content. To explain this phenomenon,a two-dimensional symmetric model was developed to simulate the spatiotemporal evolution of different species and calculate the electric thrust. The discharge morphology evolution directly corresponds to the excited-state atomic reduction process. The electric thrust on the charged particles mainly determines the reaction region and strongly influences the U-shaped formation.When the gap is less than 2 mm, the electric thrust is homogeneous throughout the entire region,resulting in a columnar shape. However, when the gap is larger than 2 mm or O_(2)is added, the electric thrust in the edge region becomes greater than that in the middle, leading to the U-shaped formation. Furthermore, in He PDBD, the charged particles generating electric thrust are mainly electrons and helium ions, while in He/O_(2)PDBD those that generate electric thrust at the outer edge of the electrode surface are mainly various oxygen-containing ions.

关键词： low-temperature plasma dielectric barrier discharge discharge morphology particle distribution electric thrust

Fragility crossover mediated by covalent-like electronic interactions in metallic liquids

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Materials Futures

Materials Futures 2024年第2期3卷 117-130页

作者： Hui-Ru Zhang Liang Gao Yu-Hao Ye Jia-Xin Zhang Tao Zhang Qing-Zhou Bu Qun Yang Zeng-Wei Zhu Shuai Wei Hai-Bin Yu wuhan national high magnetic field center and School of physics Huazhong University of Science and TechnologyWuhan 430074People’s Republic of China Department of Chemistry Aarhus University8000 AarhusDenmark iMAT Centre for Integrated Materials Research Aarhus University8000 AarhusDenmark

Fragility is one of the central concepts in glass and liquid sciences,as it characterizes the extent of deviation of viscosity from Arrhenius behavior and is linked to a range of glass properties.However,the intervention of crystallization often prevents the assessment of fragility in poor glass-formers,such as supercooled metallic liquids.Hence experimental data on their compositional dependence are scarce,let alone fundamentally understood.In this work,we use fast scanning calorimetry to overcome this obstacle and systematically study the fragility in a ternary La–Ni–Al system,over previously inaccessible composition space.We observe fragility dropped in a small range with the Al alloying,indicating an alloying-induced fragility crossover.We use x-ray photoelectron spectroscopy,resistance measurements,electronic structure calculations,and DFT-based deep-learning atomic simulations to investigate the cause of this fragility drop.These results show that the fragility crossover can be fundamentally ascribed to the electronic covalency associated with the unique Al–Al interactions.Our findings provide insight into the origin of fragility in metallic liquids from an electronic structure perspective and pave a new way for the design of metallic glasses.

关键词： metallic glass fragility fast scanning calorimetry density functional theory deep learning potential

Enhanced anomalous Hall effect in kagome magnet YbMn_(6)Sn_(6)with intermediate-valence ytterbium

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Chinese physics B 2024年第5期33卷 43-50页

作者：李龙飞迟晟玮马文龙郭凯臻徐刚贾爽 International center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China wuhan national high magnetic field center and School of physics Huazhong University of Science and TechnologyWuhan 430074China Interdisciplinary Institute of Light-Element Quantum Materials and Research center for Light-Element Advanced Materials Peking UniversityBeijing 100871China Hefei national Laboratory Hefei 230088China

We report on the magnetization and anomalous Hall effect(AHE)in the high-quality single crystals of the kagome magnet YbMn_(6)Sn_(6),where the spins of the Mn atoms in the kagome lattice order ferromagnetically and the intermediate-valence Yb atoms are nonmagnetic.The intrinsic mechanism plays a crucial role in the AHE,leading to an enhanced anomalous Hall conductivity(AHC)compared with the other rare-earth RMn_(6)Sn_(6)compounds.Our band structure calculation reveals a strong hybridization between the 4f electrons of Yb and conduction electrons.

关键词： anomalous Hall effect kagome magnet intermediate valence

Engineering Quantum Criticality for Quantum Dot Power Harvesting

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Chinese physics Letters 2024年第2期41卷 14-25页

作者：王金义年磊磊吕京涛 School of physics and Astronomy Yunnan UniversityKunming 650091China School of physics Institute for Quantum Science and Engineeringand Wuhan National High Magnetic Field CenterHuazhong University of Science and TechnologyWuhan 430074China

Coupling of quantum-dot circuits to microwave photons enables us to investigate photon-assisted quantum transport.Here,we revisit this typical circuit quantum electrodynamical setup by introducing the Kerr nonlinearity of photons.By exploiting quantum critical behavior,we propose a powerful scheme to control the power-harvesting efficiency in the microwave regime,where the driven-dissipative optical system acts as an energy pump.It drives electron transport against a load in the quantum-dot circuit.The energy transfer and,consequently,the harvesting efficiency are enhanced near the critical point.As the critical point moves towards to low input power,high efficiency within experimental parameters is achieved.Our results complement fundamental studies of photon-to-electron conversion at the nanoscale and provide practical guidance for designs of integrated photoelectric devices through quantum criticality.

关键词： quantum critical microwave

Purity-dependent Lorenz number,electron hydrodynamics and electron-phonon coupling in WTe

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Science China(physics,Mechanics & Astronomy) 2024年

作者： Wei Xie Feng Yang Liangcai Xu Xiaokang Li Zengwei Zhu Kamran Behnia wuhan national high magnetic field center and School of physics Huazhong University of Science and Technology Laboratoire de Physique et d' E'tude des Mate'riaux (ESPCI-CNRS-Sorbonne Universite') PSL University

We present a study of electrical and thermal transport in Weyl semimetal WTe2down to 0.3 K.The Wiedemann-Franz law holds below 2 K and a downward deviation starts above.The deviation is more pronounced in cleaner samples,as expected in the hydrodynamic picture of electronic transport,where a fraction of electron-electron collisions conserve momentum.Phonons are the dominant heat carriers and their mean-free-path does not display a Knudsen minimum.This is presumably a consequence of weak anharmonicity,as indicated by the temperature dependence of the specific heat.Frequent momentum exchange between phonons and electrons leads to quantum oscillations of the phononic thermal conductivity.Bloch-Gru¨neisen picture of electron-phonon scattering breaks down at low temperature when Umklapp ph-ph collisions cease to be a sink for electronic flow of momentum.Comparison with semi-metallic Sb shows that normal ph-ph collisions are amplified by anharmonicity.In both semimetals,at cryogenic temperature,e-ph collisions degrade the phononic flow of energy but not the electronic flow of momentum.

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Enhanced conductivity and weakened magnetism in Pb-doped Sr2IrO4

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Chinese physics B 2024年第1期33卷 696-701页

作者：岳智来甄伟立牛瑞焦珂珂朱文卡皮雳张昌锦 high magnetic field Laboratory Hefei Institutes of Physical ScienceChinese Academy of Sciences Science Island Branch of Graduate School University of Science and Technology of China Collaborative Innovation center of Advanced Microstructures Nanjing University

Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr2IrO4. It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0.3 in Sr2-xPbxIrO4. The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr2IrO4matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x=0.2.The present results give a fresh material base to explore new physics in doped Sr2IrO4systems.

关键词： conductivity doping iridates magnetism

Revisit of the anisotropic vortex states of 2H-NbSe_(2) towards the zero-field limit

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Chinese physics B 2024年第6期33卷 80-86页

作者：张凡侯兴元姜宇轩张宗源涂玉兵朱相德陈根富单磊 Beijing national Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China center of Free Electron Laser and high magnetic field Anhui UniversityHefei 230601China Information Materials and Intelligent Sensing Laboratory of Anhui Province Institutes of Physical Science and Information TechnologyAnhui UniversityHefei 230601China Key Laboratory of Structure and Functional Regulation of Hybrid Materials in Anhui University Ministry of EducationHefei 230601China School of physics and Materials Science Anhui UniversityHefei 230601China Anhui Key Laboratory of Condensed Matter physics at Extreme Conditions High Magnetic Field LaboratoryHFIPSAnhuiChinese Academy of Sciencesand University of Science and Technology of ChinaHefei 230031China Hefei national Laboratory Hefei 230088China

We revisited the vortex states of 2H-NbSe_(2) towards zero fields by a low-temperature scanning tunneling microscope.Fine structures of the anisotropic vortex states were distinguished, one is a spatially non-splitting zero bias peak, and the other is an in-gap conductance anomaly resembling evolved crossing features around the center of the three nearest vortices.Both of them distribute solely along the next nearest neighboring direction of the vortex lattice and become unresolved in much higher magnetic fields, implying an important role played by the vortex–vortex interactions. To clarify these issues,we have studied the intrinsic vortex states of the isolated trapped vortex in zero fields at 0.45 K. It is concluded that the anisotropic zero bias peak is attributed to the superconducting gap anisotropy, and the spatially evolved crossing features are related to the vortex–vortex interaction. The vortex core size under the zero-field limit is determined. These results provide a paradigm for studying the inherent vortex states of type-II superconductors especially based on an isolated vortex.

关键词： vortex states zero-bias conductance peak scanning tunneling microscopy

Enhanced resonance frequency in Co2FeAl thin film with different thicknesses grown on flexible graphene substrate

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Chinese physics B 2024年第3期33卷 618-622页

作者：周偲袁少康朱登玉白宇明王韬刘福福潘禄禄冯存芳张博涵何大平汪胜祥 Hubei Engineering and Technology Research center for Functional Fiber Fabrication and Testing Wuhan Textile UniversityWuhan 430200China School of Electronic and Electrical Engineering Wuhan Textile UniversityWuhan 430200China School of Mathematical and Physical Sciences Wuhan Textile UniversityWuhan 430200China School of Integrated Circuits Huazhong University of Science and TechnologyWuhan 430074China Key Laboratory for Magnetism and magnetic Materials Ministry of EducationLanzhou UniversityLanzhou 730000China Beijing national center for Condensed Matter physics and Institute of physics Chinese Academy of SciencesBeijing 100190China Hubei Engineering Research center of RF-Microwave Technology and Application Wuhan University of TechnologyWuhan 430070China

The flexible materials exhibit more favorable properties than most rigid substrates in flexibility,weight saving,mechanical reliability,and excellent environmental toughness.Particularly,flexible graphene film with unique mechanical properties was extensively explored in high frequency devices.Herein,we report the characteristics of structure and magnetic properties at high frequency of Co2FeAl thin film with different thicknesses grown on flexible graphene substrate at room temperature.The exciting finding for the columnar structure of Co2FeAl thin film lays the foundation for excellent high frequency property of Co2FeAl/flexible graphene structure.In-plane magnetic anisotropy field varying with increasing thickness of Co2FeAl thin film can be obtained by measurement of ferromagnetic resonance,which can be ascribed to the enhancement of crystallinity and the increase of grain size.Meanwhile,the resonance frequency which can be achieved by the measurement of vector network analyzer with the microstrip method increases with increasing thickness of Co2FeAl thin film.Moreover,in our case with graphene film,the resonance magnetic field is quite stable though folded for twenty cycles,which demonstrates that good flexibility of graphene film and the stability of high frequency magnetic property of Co2FeAl thin film grown on flexible graphene substrate.These results are promising for the design of microwave devices and wireless communication equipment.

关键词： enhanced resonance frequency magnetic resonance field flexible graphene substrate