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Highly in-plane anisotropy of thermal transport in suspended ternary chalcogenide Ta_(2)NiS_(5)

Nano Research 2022年第7期15卷 6601-6606页

作者： Yue Su Chuyun Deng Jinxin Liu Xiaoming Zheng Yuehua Wei Yangbo Chen Wei Yu Xiao Guo Weiwei Cai Gang Peng Han Huang Xueao Zhang College of Physical Science and Technology Xiamen UniversityXiamen 361005China College of Arts and Sciences National University of Defense TechnologyChangsha 410073China College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China Jiujiang Research Institute of Xiamen University Jiujiang 332105China Hunan Key Laboratory of Super-microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China

Energy dissipation has always been an attention-getting issue in modern electronics and the emerging low-symmetry two-dimensional(2D)materials are considered to have broad prospects in solving the energy dissipation *** the thermal transport of a typical 2D ternary chalcogenide Ta_(2)NiS_(5) is *** the first time we have observed strongly anisotropic in-plane thermal conductivity towards armchair and zigzag axes of suspended few-layer Ta_(2)NiS_(5) flakes through Raman *** 7-nm-thick Ta_(2)NiS_(5) flakes,theκz i g z a g is 4.76 W·m^(−1)·K^(−1) andκa r m c h a i r is 7.79 W·m^(−1)·K^(−1),with a large anisotropic ratio(κa r m c h a i r/κz i g z a g)of 1.64 mainly ascribed to different phonon mean-free-paths along armchair and zigzag ***,the thickness dependence of thermal anisotropy is also *** the flake thickness increases,theκa r m c h a i r/κz i g z a g reduces sharply from 1.64 to *** could be attributed to the diversity in phonon boundary scattering,which decreases faster in zigzag direction than in armchair *** anisotropic property enables heat flow manipulation in Ta_(2)NiS_(5) based devices to improve thermal management and device *** work helps reveal the anisotropy physics of ternary transition metal chalcogenides,along with significant guidance to develop energy-efficient next generation nanodevices.

关键词： anisotropic thermal conductivity ternary transition metal chalcogenide Ta_(2)NiS_(5) energy dissipation phonon mode

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Hidden self-duality in quasiperiodic network models

arXiv

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arXiv 2024年

作者： Hu, Hai-Tao Lin, Xiaoshui Guo, Ai-Min Lin, Zijing Gong, Ming Department of Physics University of Science and Technology of China Anhui Hefei230026 China Hefei National Laboratory University of Science and Technology of China Hefei230088 China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China

Mobility edges (MEs), which separate the extended phases from the localized phases, are one of the most crucial concepts in Anderson localization. In one-dimensional quasiperiodic systems, only a few models with exact MEs can be constructed using the generalized self-dual theory, the Avila’s global theory, or the renormalization groups method. Then, an intriguing question is that can we realize much more physical models with exact solvable MEs? Here we uncover the hidden self-duality in a class of quasiperiodic network models constituted by periodic sites and quasiperiodic sites. While the original models do not have self-duality, after integrating out the periodic sites, the effective Hamiltonian with energy dependent potentials will have this duality, yielding MEs. The mosaic models studied in the literature are the simplest quasiperiodic netowork models. For a long time the MEs in these models are believed to come from the absent of self-duality, and we show that they actually come from the hidden self-duality. Finally, we extend this idea to more network models and explicitly determine their exact MEs with the hidden duality. The predictions in these models can be realized using optical and acoustic waveguide arrays and electric circuits in experiments. The new models presented in this work can greatly advance our understanding of MEs in Anderson transition. Copyright © 2024, The Authors. All rights reserved.

关键词： Hamiltonians

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Resonant tunneling in disordered borophene nanoribbons with line defects

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npj Computational Materials 2022年第1期8卷 1230-1237页

作者： Pei-Jia Hu Si-Xian Wang Xiao-Feng Chen Zeng-Ren Liang Tie-Feng Fang Ai-Min Guo Hui Xu Qing-Feng Sun Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha410083China School of Physical Science and Technology Lanzhou UniversityLanzhou730000China School of Sciences Nantong UniversityNantong226019China International Center for Quantum Materials School of PhysicsPeking UniversityBeijing100871China Collaborative Innovation Center of Quantum Matter Beijing100871China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing100190China

Recently,borophene has attracted extensive interest as the wonder material,showing that line defects(LDs)occur widely at the interface between V_(1/5)and V_(1/6)boron ***,we study theoretically the electron transport through two-terminal disordered borophene nanoribbons(BNRs)with random distribution of *** results indicate that LDs strongly affect the electron transport properties of *** V_(1/5)and V_(1/6)BNRs exhibit metallic behavior without any LD,in agreement with *** in the presence of LDs,the overall electron transport ability is dramatically decreased,but some resonant peaks of conductance quantum are found in the transmission spectrum of any disordered BNR with arbitrary arrangement of *** disordered BNRs exhibit metal-insulator transition with tunable transmission gap in the insulating ***,two evolution phenomena of resonant peaks are revealed for disordered BNRs with different *** results may help for understanding structure-property relationships and designing LD-based nanodevices.

关键词： tunneling boron resonant

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Enhanced Dielectric Loss in N-Doped 3d Porous Carbon for Microwave Absorption

SSRN

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SSRN 2023年

作者： Ma, Lei Wu, Yueyang Wu, Zhiwei Xia, Pengkun He, Yuxin Zhang, Lin Fan, Hui Tong, Chuanjia Zhang, Long Gao, Xiaohui Deng, Lianwen Hunan Provincial Key Laboratory for Super-Microstructure and Ultrafast Process School of Physics and Electronics Central South University Changsha410083 China Hunan Provincial Key Laboratory for Advanced Materials For New Energy Storage nad Conversion School of Materials Science and Engineering Hunan University of Science and Technology Xiangtan411201 China

In this work, a three-dimensional porous carbon structure was in situ constructed by connecting carbon polyhedrons with graphitic nanosheets. The rich pores, high nitrogen doping content and abundant defects formed on the surface provided multiple antennas for electromagnetic wave absorption. The optimized reflection loss of the material was as low as -41.65 dB with the effective absorption band of 5.84 GHz, covering the whole Ku band. Mechanistic investigation from density functional theory calculations and electrochemical analysis showed that dipole loss and conduction loss were mainly caused by pyrrolic nitrogen and the higher electron mobility in the prepared materials. At the same time, there is a balance between conduction loss and polarization loss, which cooperatively adjusts the absorbing properties of materials. Furthermore, the material’s potential practical application performance evaluated by computer simulation technology (CST) presented that the simulated RCS values were all lower than 20 dBm2. Thus, this work enlightens new insights and methods for understanding of the microwave absorption properties of the carbon-materials. © 2023, The Authors. All rights reserved.

关键词： Dielectric losses

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Anisotropic 2D materials for post-Moore photoelectric devices

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Journal of Semiconductors 2022年第1期43卷 1-3页

作者： Dingdong Xie Jie Jiang Liming Ding Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Center for Excellence in Nanoscience(CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication(CAS)National Center for Nanoscience and TechnologyBeijing 100190China

Since the discovery of two-dimensional(2D)graphene[1],2D materials have been widely investigated due to their in-triguing physical/chemical property and outstanding optoelec-tronic performance[1−3].Generally,2D materials can be di-vided into isotropy and anisotropy according to crystal *** isotropic 2D materials like graphene and hexagon-al boron nitride,they have obvious lattice ***-as,anisotropic 2D materials possess strong anisotropic crys-tal structure(Fig.1(a)),providing new degree of freedom for exploring 2D ***,2D materials with high aniso-tropy,due to their anisotropic electrical,optical,thermal,and phonon properties,are finding applications in polarization-sensitive photodetection,neural network construction,spin-polarized transport and other emerging fields[3−6].

关键词： anisotropic struc boron

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Orbital contribution to the regulation of the spin-valley coupling in antiferromagnetic monolayer MnPTe3

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Physical Review B 2023年第3期107卷 035139-035139页

作者： Wenzhe Zhou Guibo Zheng Aolin Li Dehe Zhang Fangping Ouyang School of Physics and Electronics Hunan Key Laboratory for Super-Microstructure and Ultrafast Process and Hunan Key Laboratory of Nanophotonics and Devices Central South University Changsha 410083 People's Republic of China School of Physics and Technology State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources Xinjiang University Urumqi 830046 People's Republic of China State Key Laboratory of Powder Metallurgy and Powder Metallurgy Research Institute Central South University Changsha 410083 People's Republic of China

In addition to the ferromagnetic materials with inversion symmetry breaking, the symmetric antiferromagnetic materials also exhibit intrinsic valley splitting due to the spin-valley coupling. Using first-principles calculations, we investigated the manipulation of valley splitting of antiferromagnetic monolayer MnPTe3 via biaxial strain. It is shown that two MnPTe3 monolayers with different structures are both stable antiferromagnetic semiconductors, and exhibit valley splitting between K and K′. The spin-valley coupling strength can be greatly tuned by in-plane strain, which is due to the changes of orbital composition of electronic state and the different contribution of two sublattice atoms. The proportions of d orbitals of Mn atoms determine the orbital angular momentum of the electronic state, and the different contribution of different sublattices results in the change of Berry curvature at K and K′ points. The combination of two factors leads to the same changes of valley splitting and the proportion of the dxz, dyz orbitals. These results of are some significance for the design of materials with greater valley splitting and the understanding of its mechanism.

关键词： Spin-orbit coupling Valleytronics Antiferromagnets Monolayer films First-principles calculations

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A first-principles study on zigzag phosphorene nanoribbons terminated by transition metal atoms

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Chinese Physics B 2021年第2期30卷 476-480页

作者： Shuai Yang Zhiyong Wang Xueqiong Dai Jianrong Xiao Mengqiu Long College of Science Guilin University of TechnologyGuilin 541008China Modern Education Technology Center Guilin University of TechnologyGuilin 541008China Hunan Key Laboratory of Super Micro-structure and Ultrafast Process Central South UniversityChangsha 410083China

We have investigated the electronic and magnetic properties of zigzag phosphorene nanoribbons(ZPNRs)with transition metal(TM)passivated atoms,it can be found that the ZPNRs with TM passivated atoms exhibit different magnetisms except for the Ni-passivated ***,the results show that the magnetic moments of ZPNRs with TM passivated atoms are larger than that of ZPNRs with other passivated non-metals/***,it can be found that Fe-passivated ZPNR exhibits magnetic semiconducting character,which provides the possbility for the application of phosphorene in information *** Mn-passivated ZPNRs,it exhibits the *** results may be useful for potential applications of phosphorene in electronic and high-performance spintronic devices.

关键词： phosphorene first-principles calculations half-metallicity passivated

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Cascaded plasmonic nanorod antenna for large broadband local electric field enhancement

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Chinese Physics B 2019年第10期28卷 535-540页

作者： Dou Zhang Zhong-Jian Yang Jun He Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South University

We propose a cascaded plasmonic nanorod antenna for large broadband electric near-field enhancement. The structure has one big gold nanorod on each side of a small two-wire antenna which consists of two small gold nanorods. For each small nanorod, the enhanced and broadened optical response can be obtained due to the efficient energy transfer from its adjacent big nanorod through strong plasmonic near-field coupling. Thus, the electric field intensity of the cascaded antenna is significantly larger and broader than that of the individual small two-wire antenna. The resonant position, field intensity enhancement, and spectral width of the cascaded antenna are highly tunable by varying the geometry of the system. The quantum efficiency of the cascaded antenna is also greatly enhanced compared with that of the small antenna. Our results are important for the applications in field-enhanced spectroscopy.

关键词： surface plasmon optical antenna electric field enhancement broadband cascaded

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Symmetry and Magnetic Direction Dependent Spin/Valley Splitting and Anomalous Hall Conductivity of Antiferromagnetic Monolayer Mnpte3

SSRN

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SSRN 2024年

作者： Zhou, Wenzhe Sun, Tingyu Wan, Zhenzhen Li, Aolin Chen, Yu Ouyang, Fangping School of Physics Institute of Quantum Physics Hunan Key Laboratory for Super-Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices Central South University Changsha410083 China School of Physics and Technology State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources Xinjiang University Urumqi830046 China State Key Laboratory of Powder Metallurgy Powder Metallurgy Research Institute Central South University Changsha410083 China

Due to the time reversal symmetry breaking or spin-valley coupling, there are intrinsic valley splittings in two-dimensional magnetic materials, which are closely related to the symmetry and magnetic order. Based on MnPTe3 monolayers with different symmetries, we present an understanding of direction dependent spin/valley splitting and anomalous Hall conductivity from the perspective of orbital interactions. Unlike T-MnPTe3 with central inversion symmetry, in-plane magnetization leads to further non-degeneracy of valley electrons of H-MnPTe3, and the splitted valley states are spin polarized, which is perpendicular to the in-plane magnetization direction. The model and first-principle calculations consistently indicate that the splitting of the valley states is almost proportional to sinθxz, which originates from the difference in spin-up and spin-down interactions introduced by the breaking of spatial inversion symmetry. Regardless of spin degeneracy, non-zero anomalous Hall conductivity occurs with out-of-plane magnetization, and this direction dependent anomalous Hall effect is caused by mirror symmetry breaking from the neighboring Te atoms and spin-orbit coupling. Magnetization direction is an important means of regulating valley/spin splittings and anomalous Hall effect, which has certain significance for realizing spin or valley polarized Hall effect and the research of spintronic or valleytronic devices. © 2024, The Authors. All rights reserved.

关键词： Monolayers

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Visualizing molecular unidirectional rotation by a rotated weak-field polarization technique

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Physical Review A 2023年第6期108卷 063108-063108页

作者： Zhenzhong Lian Zhou Chen Juan Li Chuan-Cun Shu Zhan Hu Institute of Atomic and Molecular Physics Jilin University Changchun 130012 China Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Advanced Light Field and Modern Medical Treatment Science and Technology Innovation Center of Jilin Province Jilin University Changchun 130012 China

The observation of molecular rotational dynamics induced by ultrashort laser pulses is of both fundamental and practical importance. Here, we develop an extended weak-field polarization method that allows us to visualize the two-dimensional spatial rotation of molecules. By manipulating the polarization direction of the pump pulse, this method allows for characterizing the rotational dependence on the azimuth angle when a weak probe pulse is present. To demonstrate this experimental scheme, we examine two types of pump pulses: (1) a linearly polarized pulse and (2) temporally delayed double pulses polarized at an angle of π/4, which are respectively applied to gas-phase molecules N2O at room temperature. The results show that this approach effectively captures the induced impulsive alignment and unidirectional rotation. By solving the time-dependent Liouville equation governing the molecules' behavior under the influence of the polarization-skewed pump pulses, we gain further insights into the mechanisms for generating unidirectional rotation. This work holds promising potential in the detection of two- and three-dimensional rotational dynamics of molecules like enantiomers and superrotors.

关键词： Atomic & molecular processes in external fields Molecules Polarization

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