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Single pair of multi-Weyl points in nonmagnetic crystals

Physical Review B 2022年第19期106卷 195129-195129页

作者： Xiaotian Wang Feng Zhou Zeying Zhang Weikang Wu Zhi-Ming Yu Shengyuan A. Yang School of Physical Science and Technology Southwest University Chongqing 400715 China College of Mathematics and Physics Beijing University of Chemical Technology Beijing 100029 China Research Laboratory for Quantum Materials Singapore University of Technology and Design Singapore 487372 Singapore Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China

Topological semimetal states having the minimal number, i.e., only a single pair, of Weyl points are desirable for the study of effects associated with chiral topological charges. So far, the search for such states is focused on magnetic spinful systems. Here, we find that nonmagnetic spinless systems can host a class of single-pair-Weyl-point (SP-WP) states, where the two Weyl points are located at two high-symmetry time-reversal-invariant momenta. We identify 38 candidate space groups that host such states, and we show that the chiral charge of each Weyl point must be an even integer, representing a multi-Weyl point. Besides achieving the minimal number, the two points in SP-WP states are far separated in momentum space, making the physics of each individual point better exposed. The large separation combined with the even topological charge lead to extended surface Fermi loops with a noncontractible winding topology on the surface Brillouin zone torus, distinct from conventional Weyl semimetals. We confirm our proposal in the phonon spectra of two concrete materials TlBO2 and KNiIO6. Our finding applies to a wide range of systems, including electronic, phononic, and various artificial systems. It offers a new direction for the search of ideal platforms to study chiral particles.

关键词： Acoustic phonons Phonons Symmetry protected topological states Topological phases of matter Topological materials Weyl semimetal Density functional theory k dot p method

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Two-photon imaging of rabbit mammary tissue with 3D reconstruction

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Optik 2024年 309卷

作者： Liu, Meng Hou, Guozhong Li, Yuan Deng, Yanyan Zhang, Yuan Wang, Xiaofeng Xu, Chang Song, Kaiyuan Liu, Xinlong Xia, Yuanqin Zhang, Yong Hebei University of Technology Hebei Key Laboratory of Advanced Laser Technology and Equipment School of Science Tianjin300401 China Research Center for Humanoid Sensing Research Institute of Intelligent Sensing Zhejiang Lab Hangzhou311100 China Cangzhou Normal University School of Physics and Information Engineering Cangzhou061001 China Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing100190 China

A broadband two-photon fluorescence (TPF) imaging system, based on a femtosecond oscillator, has been constructed. This system enables TPF imaging of rabbit mammary gland tissue samples by detecting TPF signals generated from the tissue upon excitation by broadband femtosecond pulses. Specifically, TPF imaging utilizes a detection window of 565–615 nm to capture TPF signals from the fluorescent adenine dinucleotide (FAD) present in lactating cells within breast tissue. Moreover, the 3D reconstruction algorithm has been optimized to visualize the 3D structure of the rabbit mammary gland acinar *** optimized three-dimensional reconstruction algorithm can reduce ambiguous signal regions, making the reconstructed three-dimensional structure more reliable and accurate. This is of significant importance for studying the microscopic structure and cell distribution of breast tissue, contributing to a deeper understanding of the tissue's physiological status. © 2024 Elsevier GmbH

关键词： Tissue

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Theoretical studies of bound configuration levels and their radiative lifetimes in Pd− and Pt−

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Physical Review A 2022年第6期106卷 062820-062820页

作者： C. X. Song S. J. Wu K. Wang X. M. Zhang R. Si C. Y. Chen Shanghai EBIT Lab Key Laboratory of Nuclear Physics and Ion-beam Application Institute of Modern Physics Department of Nuclear Science and Technology Fudan University Shanghai 200433 China Department of Physics and Anhui Key Laboratory of Optoelectric Materials Science and Technology Key Laboratory of Functional Molecular Solids Ministry of Education Anhui Normal University Wuhu Anhui 241000 China

We performed multiconfiguration Dirac-Hartree-Fock and relativistic configuration-interaction calculations for states of the 4d95s2 and 4d105s configurations in Pd− and for states of the 5d96s2 and 5d106s configurations in Pt−. Valence-valence, core-valence, and core-core electron correlation effects are accounted for in the present studies. The calculated excited energy levels agree within 2.5% with the available experimental values for both Pd− and Pt− and we confirm that Pd− only has one bound excited state. We report a more precise value for the radiative lifetime of 5d96s22D3/2 in Pt− (67.0±0.3 ms), which agrees within the experimental range (50–200 ms), but the radiative lifetime of 5d106s2S1/2 (4.00±0.16 s) in Pt− is 50% longer than the experimental measurement (2.54±0.10 s). The radiative lifetimes for 4d95s22D3/2,5/2 in Pd− are also discussed in detail.

关键词： Atomic & molecular structure Atomic spectra Electronic structure of atoms & molecules

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Ultra-high speed random bit generation based on Rayleigh feedback assisted ytterbium-doped random fiber laser

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science China(Technological sciences) 2021年第6期64卷 1295-1301页

作者： WU Han XIONG Ji HAN Bing WANG ZiNan ZHANG WeiLi JIA XinHong LIANG HouKun College of Electronics and Information Engineering Sichuan UniversityChengdu 610064China Key Lab of Optical Fiber Sensing&Communications University of Electronic Science&Technology of ChinaChengdu 611731China School of Physics and Electronic Engineering Sichuan Normal UniversityChengdu 610101China

In this paper, we propose an ultra-high speed random bit generator without the time-delay signature based on an ytterbium-doped random fiber laser(YRFL) with Rayleigh scattering feedback. The spectrum of the YRFL has a relatively broad bandwidth(0.35 nm) and the lasing temporal intensity shows random fluctuations without cavity induced time-delay signatures(TDS),which are essential for ultra-high speed random bit generation. The chaotic signal and its time-delayed signal sampling at40 Giga samples per second(GS/s) are converted to digital 8-bit signals. By selecting 5 least significant bits from each 8-bit digital signal and using bitwise exclusive-OR operation, we experimentally achieve 200 Gbps physical random bit generation based on ytterbium-doped random fiber laser with the verified randomness. The combination of broadband emission and free of TDS makes random fiber lasers new promising sources for high performance random bit generation in a simple and compact configuration, which has a great potential in cryptography and secure communication applications.

关键词： random fiber laser Rayleigh scattering random bit generation random laser

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Structural, mechanical, electronic properties, and Debye temperature of quaternary carbide Ti3NiAl2C ceramics under high pressure: A first-principles study

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Chinese physics B 2021年第3期30卷 416-422页

作者： Diyou Jiang Wenbo Xiao Sanqiu Liu Key Laboratory of Nondestructive Testing Ministry of EducationNanchang Hangkong UniversityNanchang 330063China Fujian Science&Technology Innovation Laboratory for Energy Devices of China(21C-LAB) Ningde 352100China Department of Physics Nanchang UniversityNanchang 330047China

Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural *** this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye *** carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–***,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds *** the pressure reaches 20 GPa,the covalent bonds change to metallic *** volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at *** can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C *** 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ***,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing *** addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.

关键词： quaternary carbide Ti3NiAl2C ceramics structural properties mechanical properties electronic properties Debye temperature first-principles

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Stationary states of forced two-phase turbulence

arXiv

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arXiv 2025年

作者： Jain, Suhas S. Elnahhas, Ahmed Flow Physics and Computational Science Lab George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology GA United States Center for Turbulence Research Stanford University CA United States

In this work, we perform numerical simulations of forced two-phase isotropic turbulence to study the stationary states of a two-phase mixture. We first formulate three different approaches to force a two-phase turbulent flow that maintains a constant (a) mixture kinetic energy, (b) mixture kinetic energy + surface energy, and (c) individual phase kinetic energy, and study their effect on the final stationary state of the system. We show that forcing the two-phase system eliminates the arbitrariness associated with the initialization of the second phase in two-phase turbulence simulations. Next, we study the global statistics of the two-phase mixture in the stationary state for varying density ratios (10−3 to 103) and viscosity ratios (10−3 to 103), void fraction (dilute to dense regimes), and Weber numbers (breakup and non-breakup regimes). We utilize a spatial filtering approach, that is applicable for the general case of incompressible/compressible two-phase flows, to compute the energy spectra of each of the phases and study the turbulent kinetic energy distribution across scales. We find that the interface behaves as a soft wall, inhibiting the accommodation of eddies inside the dispersed phase. Finally, we show that bubbles and drops exhibit different turbulent characteristics for the same global conditions of the carrier phase, with bubbles exhibiting higher turbulent intensities inside them and droplets behaving ballistically, similar to solid particles. This study acts as a foundational work on stationary two-phase turbulence, which can be used for further analysis and the development of subgrid-scale models for larger-scale simulations of two-phase turbulent flows. © 2025, CC BY.

关键词： Wakes

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Quantum-based Variational Approach for Solving Graph Isomorphism Problems

arXiv

引用

arXiv 2025年

作者： Wang, Yukun Shen, Yingtong Zhang, Zhichao Wan, Linchun Beijing Key Laboratory of Petroleum Data Mining China University of Petroleum Beijing102249 China State Key Lab of Processors Institute of Computing Technology CAS Beijing100190 China School of Mathematics and Physics University of Science and Technology Beijing Beijing100083 China School of Computer and Information Science Southwest University Chongqing400715 China

The graph isomorphism problem remains a fundamental challenge in computer science, driving the search for efficient decision algorithms. Due to its ambiguous computational complexity, heuristic approaches such as simulated annealing are frequently used to explore the solution space selectively. These methods often achieve high probabilities of identifying solutions quickly, avoiding the exhaustive enumeration required by exact algorithms. However, traditional simulated annealing usually struggles with low sampling efficiency and reduced solution-finding probability in complex or large graph problems. In this study, we integrate the principles of quantum technology to address the graph isomorphism problem. By mapping the solution space to a quantum many-body system, we developed a parameterized model for variational simulated annealing. This approach emphasizes the regions of the solution space that are most likely to contain the optimal solution, thereby enhancing the search accuracy. Artificial neural networks were utilized to parameterize the quantum many-body system, leveraging their capacity for efficient function approximation to perform accurate sampling in the intricate energy landscapes of large graph problems. Copyright © 2025, The Authors. All rights reserved.

关键词： Heuristic methods

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Twisted Heating-Cooling Transition of Near-field Radiation in Drifted Metasurfaces

arXiv

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arXiv 2023年

作者： Peng, Jiebin Wang, Zi Ren, Jie Center for Phononics and Thermal Energy Science China-EU Joint Lab on Nanophononics Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology School of Physics Science and Engineering Tongji University Shanghai200092 China School of Physics and Optoelectronic Engineering Guangdong University of Technology Guangdong Province Guangzhou510006 China

The magic angle twisted bilayer systems give rise to many exotic phenomena in two-dimensional electronic or photonic platforms. Here, we study the twisted near-field energy radiation between graphene metasurfaces with nonequilibrium drifted Dirac electrons. Anomalously, we find unconventional radiative flux that directs heat from cold to hot. This far-from-equilibrium phenomenon leads to a heating-cooling transition beyond a thermal magic twist angle, facilitated by twist-induced photonic topological transitions. The underlying mechanism is related to the spectrum match and mismatch caused by the cooperation between the non-reciprocal nature of drifted plasmon polaritons and their topological features. Furthermore, we report the unintuitive distance dependence of radiative energy flux under large twist angles. The near-field radiation becomes thermal insulating when increasing to a critical distance, and subsequently reverses the radiative flux to increase the cooling power as the distance increases further. Our results indicate the promising future of nonequilibrium drifted and twisted devices and pave the way towards tunable radiative thermal management. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology

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Wrapping dynamics and critical conditions for active nonspherical nanoparticle uptake

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Physical Review E 2023年第5期107卷 054401-054401页

作者： Ke Xiao Rui Ma Chen-Xu Wu Wenzhou Institute University of Chinese Academy of Sciences Wenzhou 325016 People's Republic of China and Department of Physics College of Physical Science and Technology Xiamen University Xiamen 361005 People's Republic of China. Fujian Provincial Key Lab for Soft Functional Materials Research Research Institute for Biomimetics and Soft Matter Department of Physics College of Physical Science and Technology Xiamen University Xiamen 361005 People's Republic of China.

The cellular uptake of self-propelled nonspherical nanoparticles (NPs) or viruses by cell membrane is crucial in many biological processes, but its universal dynamics have yet to be elucidated. In this study, using the Onsager variational principle, we obtain a general wrapping equation for nonspherical self-propelled nanoparticles. Two analytical critical conditions are theoretically found, indicating a continuous full uptake for prolate particles and a snapthrough full uptake for oblate particles. They precisely capture the full uptake critical boundaries in the phase diagrams numerically constructed in terms of active force, aspect ratio, adhesion energy density, and membrane tension. It is found that enhancing activity (active force), reducing effective dynamic viscosity, increasing adhesion energy density, and decreasing membrane tension can significantly improve the wrapping efficiency of the self-propelled nonspherical nanoparticles. These results give a panoramic view of the uptake dynamics of active nonspherical nanoparticles, and may offer instructions for designing an effective active NP-based vehicle for controlled drug delivery.

关键词： Endocytosis Mechanical deformation Cell membrane Self-propelled particles

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Final version - The Low-Voltage X, $\mathrm{K}_{\mathrm{u}}$ and W-Bands Magnetrons with Two Energy Outputs: New Possibilities

Final version - The Low-Voltage X, $\mathrm{K}_{\mathrm{u}}$...

引用

International Conference on vacuum Electronics

作者： Gennadiy Churyumov Shuang Qiu Nan-nan Wang Vacuum Electronics Department O.Ya. Usikov Institute for Radiophysics and Electronics National Academy of Science of Ukraine Kharkiv Ukraine Applied Physics Department Tsinghua University Beijing China Microwave Engineering Department Harbin Institute of Technology Harbin China

This paper presents the theoretical and experimental results of the studies of the new designs of the magnetrons known as the magnetrons with two energy outputs (or dual-output magnetrons). The prototypes of the two magnetrons for X and Ku-bands are developed. The magnetrons produce the average maximum powers of ~ 18.6 W and ~ 15.5 W, frequency tuning of ~ 220 MHz and ~ 150 MHz, and frequency stability of $(3\ldots 5)10^{-6}$ , respectively. The results of computer modeling of the W-band magnetron are presented. Examples of applying the dual-output magnetrons in radar systems and communication are given.

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