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中国真空学会2023学术年会、第十六届国际真空科学与工程应用学术会议（VSEA-16）

作者： Yi-Yang Yin Yu-Tian Zhang Yun-Peng Wang Yu-Yang Zhang Shixuan Du University of Chinese Academy of Sciences and Institute of Physics Chinese Academy of Sciences Hunan Key Laboratory for Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South University

Two-dimentional materials show intriguing properties in many aspects,including thermal transport *** and h-BN are two well-known examples among them that possess very high thermal ***,thermal transport properties of their amorphous counter parts remain unclear due to the absence of an accurate *** this work,we report calculations of the in-plane thermal conductivities of monolayer amorphous carbon（MAC） and monolayer amorphous boron nitride（ma-BN）,by reverse nonequilibrium molecular dynamics *** find that the thermal conductivities of both MAC and ma-BN are about two orders of magnitude smaller than their crystalline counter parts,and are independent of temperature and strain due to their extremely short heat carrier mean free ***,the ma-BN shows strong vibrational localization across the frequency range,while the MAC exhibits a unique extended G diffusion mode due to its sp2 hybridization and the broken Eg *** present results reveal the intrinsic low thermal conductivities of MAC and ma-BN,suggesting potential applications of these two materials in thermal management.

关键词： 2D materials amorphous thermal transport carbon boron nitride

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Visualizing vibrationally resolved attosecond time delay in resonance-enhanced multiphoton ionization of NO molecules

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Physical Review A 2023年第2期108卷 023114-023114页

作者： Xing Li Yong Liu Dongdong Zhang Lanhai He Sizuo Luo Chuan-Cun Shu Dajun Ding Institute of Atomic and Molecular Physics Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy Jilin University Changchun 130012 China Department of Physics Dalian University of Technology Dalian 116024 China Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China

We demonstrate a combined experimental and theoretical study to measure attosecond-resolved resonance-enhanced multiphoton ionization (REMPI) of NO molecules using the phase-locked strong 400-nm and weak 800-nm laser pulses. By performing the time-dependent wave-packet simulation, our results show that a vibrational-dependent REMPI occurs through two intermediate electronic states A2Σ+ and B2Π, from which a molecular wave packet at different internuclear distances results in an ionization time delay up to 630 as. We find that the nonadiabatic coupling between electronic states A2Σ+(ν=2) and B2Π(ν′=4) plays a crucial role in the angular-dependent phase variations of emitted electrons. This work extends the application of the REMPI technique to visualize the effect of vibrational motions of intermediate resonance states on the strong-field-induced ionization in attosecond timescales.

关键词： Multiphoton or tunneling ionization & excitation Stark effect Strong electromagnetic field effects Strong field excitation

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Piezovalley effect and magnetovalley coupling in altermagnetic semiconductors

arXiv

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arXiv 2024年

作者： Xie, Weifeng Xu, Xiong Yue, Yunliang Xia, Huayan Wang, Hui School of Microelectronics and Physics Hunan University of Technology and Business Changsha410205 China School of Physics Hunan Key Laboratory of Super Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices State Key Laboratory of Powder Metallurgy Central South University Changsha410083 China College of Information Engineering Yangzhou University Yangzhou225127 China

Clarifying the physical origin of valley polarization and exploring promising ferrovalley materials are conducive to the application of valley degrees of freedom in the field of information storage. Here, we explore two novel altermagnetic semiconductors (monolayers Nb2Se2O and Nb2SeTeO) with Néel temperature above room temperature based on first-principles calculations. It reveals that uniaxial strain induces valley polarization without spin-orbital coupling (SOC) in altermagnets owing to the piezovalley effect, while uniaxial compressive strain transforms the intrinsic ferrovalley semiconductor into a semimetal, half metal and metal. Moreover, moderate biaxial strain renders Janus monolayer Nb2SeTeO to robust Dirac-like band dispersion. The SOC and intrinsic in-plane magnetocrystalline anisotropy energy induce Dirac-like altermagnets to generate apparent valley polarization through magnetovalley coupling. In terms of SOC perturbation, we elucidate the physical mechanism behind in-plane-magnetization induced valley polarization and demonstrate the magnitude of valley polarization is positively correlated with the square of SOC strength and negatively correlated with the bandgap. The present work reveals the physical origin of valley polarization in altermagnets and expands the application of ferrovalley at room temperature in valleytronics. Copyright © 2024, The Authors. All rights reserved.

关键词： Magnetocrystalline anisotropy

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Anisotropic in-plane thermal conductivity for multi-layer WTe_(2)

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Nano Research 2022年第1期15卷 401-407页

作者： Yuehua Wei Chuyun Deng Xiaoming Zheng Yangbo Chen Xiangzhe Zhang Wei Luo Yi Zhang Gang Peng Jinxin Liu Han Huang Weiwei Cai Qi Ge Renyan Zhang Xueao Zhang Shiqiao Qin College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China College of Arts and Sciences National University of Defense TechnologyChangsha 410073China College of Physical Science and Technology Xiamen UniversityXiamen 361005China Hunan Key Laboratory of Super-microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Chongqing 2D Materials Institute Liangjiang New AreaChongqing 400714China

Improving thermal transport between substrate and transistors has become a vital solution to the thermal challenge in *** 2D WTe_(2) has sparked extensive interest because of heavy atomic mass and low Debye ***,the thermal transport of supported WTe_(2) was studied via Raman thermometry with electrical *** supported 30 nm WTe2 encased with 70 nm Al_(2)O_(3) delivered 4.8 W·m^(-1)·K^(-1)in-plane thermal conductivity along zigzag direction at room temperature,which was almost 1.6 times larger than that along armchair direction(3.0 W·m^(-1)·K^(-1)).Interestingly,the superior and inferior directions for thermal transport are just opposite of those for electrical ***,a heat manipulation model in WTe_(2) FET device was *** the designed configuration,waste heat in WTe_(2) would be mostly dissipated to metal contacts located along zigzag,relieving the local temperature discrepancy in the channel effectively and preventing degradation or *** study provides new insight into thermal transport of anisotropic 2D materials,which might inspire energy-efficient nanodevices in the future.

关键词： WTe_(2) anisotropy in-plane thermal conductivity Raman thermometry with electrical heating Raman spectrum

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First-principles study of spin-orbital coupling induced ferroelectricity in NiBr2

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Physical Review B 2023年第5期108卷 054429-054429页

作者： Da-Wei Wu Yong-Bo Yuan Shuang Liu Meng-Qiu Long Yun-Peng Wang School of Physics and Electronics Hunan Key Laboratory for Super-Micro Structure and Ultrafast Process Central South University 932 South Lushan Road Changsha 410083 China

Two-dimensional multiferroic materials have attracted wide interest due to their intriguing physical properties and strong electromagnetic coupling. Among them, NiBr2 is unique with a temperature dependent magnetic modulation vector Q which is linearly related to the electric polarization. In this work, we perform first-principles calculations on the NiBr2 monolayer. Density functional theory calculations with appropriate Hubbard correction reproduce the electric polarization and its linear dependence on the magnitude of Q. The calculated polarization decreases as the Hubbard parameter U increases which enlarges the electronic band gap. Our results suggest the spin-orbital coupling effect of Br ions play a crucial role in generating the polarization. Wannier function analysis proves that the major contributor to electric polarization is the Br atomic orbitals which are strongly hybridized with Ni orbitals. The atomic position relaxation has a negligible contribution to the polarization.

关键词： Ferroelectricity Multiferroics Noncollinear magnets Density functional calculations

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Temperature-Dependent Raman Spectroscopy Analysis of Single Spiral Ws2 Nanosheets with Screw Dislocations

SSRN

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SSRN 2023年

作者： Madoune, Yassine Ismail, Ayman A.A. Hunan Key Laboratory of Nanophotonic and Devices Hunan Key Laboratory of Super-microstructure and Ultrafast Process Central South University School of Physics and Electronics Hunan Changsha410083 China School of Metallurgy and Environmen engineering Central South University Changsha410083 China

This study presents Raman spectroscopy measurements of Screw Dislocation Single Spiral Pattern SDD-SSP-WS2 samples supported on SiO2/Si at various locations, including the edge, middle, and center across temperatures spanning from 80 K to 560 K. A physical model that encompasses both the temperature effect and volume effect has been employed to comprehensively comprehend the nonlinearity temperature dependence of the A_1gmode in a quantitative manner. It is shown that the four-phonon scattering and thermal expansion effect are the major causes of the Raman mode's non-linear dependency. The thermal expansion effect and four phonons positively correlate with thicknesses , while the three-phonon scattering effect has an inverse relationship. The investigation of the full width at half maximum (FWHM) of the A_1g mode has been conducted through experimental and theoretical means, utilizing various expressions within the identical temperature range. The observed broadening of FWHM A_1g mode can be attributed to the decay of the A_1gphonon. This study aims to enhance comprehension of the anharmonic characteristics and behaviors of phonons in SDD-SSP-WS2 flakes of varying thicknesses. © 2023, The Authors. All rights reserved.

关键词： Sulfur compounds

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Theoretical study of spin-orbit coupling in Janus monolayer MA2Z4 3

Theoretical study of spin-orbit coupling in Janus monolayer ...

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3rd International Conference on Advanced Material and Clean Energy, ICAMCE 2022

作者： Wu, Liang Zhou, Wenzhe Zhang, Dehe Ouyang, Fangping School of Physics and Electronics Hunan Key Laboratory for Super-Microstructure and Ultrafast Process Central South University Changsha410083 China State Key Laboratory of Powder Metallurgy Powder Metallurgy Research Institute Central South University Changsha410083 China School of Physics and Technology Xinjiang University Urumqi830046 China

In this paper, based on first-principles calculations, we investigate the energy valley and spin-orbit coupling properties of Janus monolayer MA2Z4. The stability of different structures is illustrated. Due to the breaking of mirror symmetry, Rashba splitting occurs at the "point in the band structures of Janus monolayers WSiGeN4 and WSi2(NP)2. The relationship between Rashba spin-orbit coupling strength and potential energy gradient and d-orbital composition is explored. Janus monolayer WSi2(NP)2 has stronger Rashba effect than WSiGeN4 due to the strong asymmetry of the d orbital of W atom. These results help to promote the application of two-dimensional materials in spintronics and valleytronics. © Published under licence by IOP Publishing Ltd.

关键词： Monolayers

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PT-symmetric quantum Rabi model

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Physical Review A 2023年第5期108卷 053712-053712页

作者： Xilin Lu Hui Li Jia-Kai Shi Li-Bao Fan Vladimir Mangazeev Zi-Min Li Murray T. Batchelor Institute of Quantum Physics Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Mathematical Science Institute Australian National University Canberra ACT 2601 Australia Research School of Physics Australian National University Canberra ACT 2601 Australia

In this work, we explore the PT-symmetric quantum Rabi model, which describes a PT-symmetric qubit coupled to a quantized light field. By employing the adiabatic approximation (AA), we are able to solve this model analytically in the parameter regime of interest and analyze various physical aspects. We investigate the static and dynamic properties of the model, using both the AA and numerical diagonalization. Our analysis reveals a multitude of exceptional points (EPs) that are closely connected with the exactly solvable points in the Hermitian counterpart of the model. Intriguingly, these EPs vanish and revive depending on the light-matter coupling strength. Furthermore, we discuss the time evolution of physical observables under the non-Hermitian Hamiltonian. Rich and exotic behaviors are observed in both strong and ultrastrong coupling regimes. Our work extends the theory of PT symmetry into the full quantum light-matter interaction regime and provides insights that can be readily enlarged to a broad class of quantum optical systems.

关键词： PT-symmetric quantum mechanics Quantum description of light-matter interaction Quantum optics Non-Hermitian systems PT-symmetry Rabi model Two-level models

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Exploring the regulatory effect of stacked layers on moiréexcitons in twisted WSe_(2)/WSe_(2)/WSe_(2)homotrilayer

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Nano Research 2023年第7期16卷 10573-10579页

作者： Haihong Zheng Biao Wu Chang-Tian Wang Shaofei Li Jun He Zongwen Liu Jian-Tao Wang Ji-an Duan Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South University932 South Lushan RoadChangsha 410083China State Key Laboratory of Precision Manufacturing for Extreme Service Performance Central South University932 South Lushan RoadChangsha 410083China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia The University of Sydney Nano Institute The University of SydneyNSW 2006Australia Songshan Lake Materials Laboratory Dongguan 523808China Shenzhen Research Institute of Central South University Shenzhen 518057China

Moirésuperlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional *** periodic moirépatterns generated by these structures lead to the formation of flat mini-bands,which alter the electronic energy bands of the *** resulting flat electronic bands can greatly enhance strong correlative interactions between electrons,leading to the emergence of exotic quantum phenomena,including moiréphonons and moiré*** extensive research has been conducted on the exotic quantum phenomena in twisted bilayers of transition metal dichalcogenides(TMDs),and the regulatory effect of stacked layers on moiréexcitons remains *** this study,we report the fabrication of a twisted WSe_(2)/WSe_(2)/WSe_(2) homotrilayer with two twist angles and investigate the influence of stacked layers on moiré*** experiments reveal multiple moiréexciton splitting peaks in the twisted trilayer,with moirépotential depths of 78 and 112 meV in the bilayer and trilayer homostructures,*** also observed the splitting of the moiréexcitons at 90 K,indicating the presence of a deeper moirépotential in the twisted ***,we demonstrate that stacked layers can tune the moiréexcitons by manipulating temperature,laser power,and magnetic *** results provide a new physical model for studying moirésuperlattices and their quantum properties,which could potentially pave the way for the development of quantum optoelectronics.

关键词： materials material field

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High performance Photodetector Based on PdSe2/MoS2heterojunction 3

High performance Photodetector Based on PdSe2/MoS2heterojunc...

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3rd International Conference on Advanced Material and Clean Energy, ICAMCE 2022

作者： Shi, Hongxiang Chen, Houjie Wei, Zhenhua Luo, Wei Ouyang, Fangping School of Physics and Electronics And Hunan Key Laboratory for Super-Microstructure and Ultrafast Process Central South University\ Changsha410083 China State Key Laboratory of Powder Metallurgy And Powder Metallurgy Research Institute Central South University Changsha410083 China College of Arts and Science National University of Defense Technology Changsha410073 China

Photodetectors are devices that instantaneously convert optical signals into electrical signals. With the advancement of science and technology, they are being widely used in various fields. Two-dimensional materials possess many unique and important properties, such as tunable band gap, etc., and have been widely used in photodetectors, and have been widely used in photodetectors in terms of responsivity (R), detectability (D∗) and external quantum efficiency (EQE) Shows excellent performance. By building heterojunctions, 2D materials can serve as excellent photodetector components. Herein, We prepared two-dimensional multilayer PdSe2 thin films by a simple one-step direct selenization method and a high performance photodetector was fabricated based on vertically stacked MoS2/PdSe2 heterojunctions via a Van der Waals force mechanical transfer method. The fabricated device displays current rectification characteristics in darkness (on/off ratio > 102) and superior photovoltaic behavious under illumination. In addition, the MoS2/PdSe2 heterojunctions exhibits a remarkable responsivity of 2.7A·W-1 and a fast response time at 193/96 μs under 532nm laser irradiation. These results provide new opportunities for developing highly responsive and high-speed photodetectors to address integrated applications. © Published under licence by IOP Publishing Ltd.

关键词： Van der Waals forces

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