None Fan Xiao-Zheng, None Li Yi-Lian, None Wu Yi, None Chen Jun-Cai, None Xu Guo-Liang, None An Yi-Peng
Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb3Cl8 monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb3Cl8 monolayer. We also further construct its p-n junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb3Cl8 monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb3Cl8 monolayer is 0.997 μB, and its easy magnetization axis is in the plane and along the x axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb3Cl8 monolayer to flip vertically from in-plane to out-plane. The designed p-n junction diode nanodevice based on Nb3Cl8 monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb3Cl8 monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.
{"title":"Magnetic and spin transport properties of a two-dimensional magnetic semiconductor kagome lattice Nb<sub>3</sub>Cl<sub>8</sub> monolayer","authors":"None Fan Xiao-Zheng, None Li Yi-Lian, None Wu Yi, None Chen Jun-Cai, None Xu Guo-Liang, None An Yi-Peng","doi":"10.7498/aps.72.20231163","DOIUrl":"https://doi.org/10.7498/aps.72.20231163","url":null,"abstract":"Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb<sub>3</sub>Cl<sub>8</sub> monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb<sub>3</sub>Cl<sub>8</sub> monolayer. We also further construct its <i>p-n</i> junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer is 0.997 μ<sub>B</sub>, and its easy magnetization axis is in the plane and along the <i>x</i> axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer to flip vertically from in-plane to out-plane. The designed <i>p-n</i> junction diode nanodevice based on Nb<sub>3</sub>Cl<sub>8</sub> monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb<sub>3</sub>Cl<sub>8</sub> monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136053404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Yang Rui-Long, None Zhang Yu-Ying, None Yang Ke, None Jiang Qi-Tao, None Yang Xiao-Ting, None Guo Jin-Zhong, None Xu Xiao-Hong
Two-dimensional magnetic materials are emerging materials developed in recent years and have attracted much attention for their unique magnetic properties and structural features in single or few layers of atomic thickness. Among them, ferromagnetic materials have a wide range of applications such as information memory and processing. Therefore the current research is mainly focused on enriching the two-dimensional ferromagnetic database and developing modification strategies for magnetic modulation. In this paper, two-dimensional vanadium-doped Cr2S3nanosheets were successfully grown on mica substrates by atmospheric pressure chemical vapour deposition. The thickness and size of the nanosheets can be effectively regulated by changing the temperature and mass of vanadium source VCl3 powders, with the temperature of 765℃ and the mass of 0.010 g as the most appropriate conditions for the growth of nanosheets. The nanosheets were also characterised by optical microscopy, atomic force microscopy, raman spectroscopy, scanning electron microscopy, X-ray energy spectroscopy, X-ray photoelectron spectroscopy, and the nanosheets were regular in shape, with flat surfaces and controllable thicknesses, and high quality vanadium-doped Cr2S3 nanosheets were prepared. Meanwhile, the magnetic characterisation of the doped samples showed that the Curie transition temperature of the vanadium doped samples changed to 105 K, and the maximum magnetic moment point of 75 K in the M-T curve disappeared after V doping, and from subferromagnetic to ferromagnetic, and the coercivity in the M-H curve also increased significantly, which proved that the vanadium doping could effectively regulate the magnetic properties of Cr2S3 nanosheets. These results are expected to advance the possibility of vanadium-doped Cr2S3 materials toward practical applications and become one of the ideal candidate material for next generation spintronic applications.
{"title":"Growth and magnetic properties of two-dimensional vanadium-doped Cr<sub>2</sub>S<sub>3</sub> nanosheets","authors":"None Yang Rui-Long, None Zhang Yu-Ying, None Yang Ke, None Jiang Qi-Tao, None Yang Xiao-Ting, None Guo Jin-Zhong, None Xu Xiao-Hong","doi":"10.7498/aps.73.20231229","DOIUrl":"https://doi.org/10.7498/aps.73.20231229","url":null,"abstract":"Two-dimensional magnetic materials are emerging materials developed in recent years and have attracted much attention for their unique magnetic properties and structural features in single or few layers of atomic thickness. Among them, ferromagnetic materials have a wide range of applications such as information memory and processing. Therefore the current research is mainly focused on enriching the two-dimensional ferromagnetic database and developing modification strategies for magnetic modulation. In this paper, two-dimensional vanadium-doped Cr<sub>2</sub>S<sub>3</sub>nanosheets were successfully grown on mica substrates by atmospheric pressure chemical vapour deposition. The thickness and size of the nanosheets can be effectively regulated by changing the temperature and mass of vanadium source VCl<sub>3</sub> powders, with the temperature of 765℃ and the mass of 0.010 g as the most appropriate conditions for the growth of nanosheets. The nanosheets were also characterised by optical microscopy, atomic force microscopy, raman spectroscopy, scanning electron microscopy, X-ray energy spectroscopy, X-ray photoelectron spectroscopy, and the nanosheets were regular in shape, with flat surfaces and controllable thicknesses, and high quality vanadium-doped Cr<sub>2</sub>S<sub>3</sub> nanosheets were prepared. Meanwhile, the magnetic characterisation of the doped samples showed that the Curie transition temperature of the vanadium doped samples changed to 105 K, and the maximum magnetic moment point of 75 K in the M-T curve disappeared after V doping, and from subferromagnetic to ferromagnetic, and the coercivity in the M-H curve also increased significantly, which proved that the vanadium doping could effectively regulate the magnetic properties of Cr<sub>2</sub>S<sub>3</sub> nanosheets. These results are expected to advance the possibility of vanadium-doped Cr<sub>2</sub>S<sub>3</sub> materials toward practical applications and become one of the ideal candidate material for next generation spintronic applications.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136054183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The aerodynamic heat of hypersonic vehicle nose cone can reach MWm-2 magnitude during flight, which could be transferred to the interior of hypersonic vehicle in the form of conduction and radiation. High efficient thermal insulation material is significant to keep internal electronic components working safely. Thermal metamaterials can regulate the macroscopic heat flow path, which have been developing rapidly and have a wide application prospect in the field of thermal protection. In this paper, a non-enclosed theoretical thermal cloak is designed to guide heat flow around hypersonic vehicle nose cone by using the transformation multithermotics, which can control thermal conduction and radiation simultaneously. A multi-layer structure is designed as cloak's simplified approximation due to the anisotropic parameters. Based on the software COMSOL, the thermal protection characteristics and heat transfer mechanism of the cloak and multi-layer structure are studied numerically. The results show that heat can flow around the object in the form of conduction and radiation in both theoretical thermal cloak and multi-layer structure, so the heat transferred to the inner area is decreased. Compared with the thermal insulation material, the heating rate of the protected area slows down, and the temperature at the front of the hypersonic vehicle nose cone is significantly reduced. However, the improvement of the thermal protection performance of cloak and multi-layer structures requires that the solid and radiative thermal conductivities of the material be lower than those of the original thermal insulation materials. To solve this problem, a non-enclosed theoretical extrapolation thermal cloak is further proposed. The solid and radiative thermal conductivities of extrapolation thermal cloak are non-singular, which could be higher than those of the original thermal insulation materials. Numerical simulation results show that the extrapolation thermal cloak can guide heat flow around object, so the thermal protection capability is improved significantly. Compared with the thermal insulation materials, the temperature of the front of the hypersonic vehicle nose cone is reduced by 100 K, and the temperature of the inner central zone of the hypersonic vehicle nose cone is reduced by 10 K. The non-enclosed extrapolation thermal cloak provides a new approach for thermal protection and is suitable for complex target areas, showing great application potential in thermal protection.
{"title":"Study on thermal protection characteristics of non-enclosed thermal cloak","authors":"None Miao Yu-Zhao, None Tang Gui-Hua","doi":"10.7498/aps.73.20231262","DOIUrl":"https://doi.org/10.7498/aps.73.20231262","url":null,"abstract":"The aerodynamic heat of hypersonic vehicle nose cone can reach MWm<sup>-2</sup> magnitude during flight, which could be transferred to the interior of hypersonic vehicle in the form of conduction and radiation. High efficient thermal insulation material is significant to keep internal electronic components working safely. Thermal metamaterials can regulate the macroscopic heat flow path, which have been developing rapidly and have a wide application prospect in the field of thermal protection. In this paper, a non-enclosed theoretical thermal cloak is designed to guide heat flow around hypersonic vehicle nose cone by using the transformation multithermotics, which can control thermal conduction and radiation simultaneously. A multi-layer structure is designed as cloak's simplified approximation due to the anisotropic parameters. Based on the software COMSOL, the thermal protection characteristics and heat transfer mechanism of the cloak and multi-layer structure are studied numerically. The results show that heat can flow around the object in the form of conduction and radiation in both theoretical thermal cloak and multi-layer structure, so the heat transferred to the inner area is decreased. Compared with the thermal insulation material, the heating rate of the protected area slows down, and the temperature at the front of the hypersonic vehicle nose cone is significantly reduced. However, the improvement of the thermal protection performance of cloak and multi-layer structures requires that the solid and radiative thermal conductivities of the material be lower than those of the original thermal insulation materials. To solve this problem, a non-enclosed theoretical extrapolation thermal cloak is further proposed. The solid and radiative thermal conductivities of extrapolation thermal cloak are non-singular, which could be higher than those of the original thermal insulation materials. Numerical simulation results show that the extrapolation thermal cloak can guide heat flow around object, so the thermal protection capability is improved significantly. Compared with the thermal insulation materials, the temperature of the front of the hypersonic vehicle nose cone is reduced by 100 K, and the temperature of the inner central zone of the hypersonic vehicle nose cone is reduced by 10 K. The non-enclosed extrapolation thermal cloak provides a new approach for thermal protection and is suitable for complex target areas, showing great application potential in thermal protection.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136054186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The energetic electron (EE) excitation of beta-induced Alfvén eigenmodes is investigated by using the newly developed global eigenvalue code MAS, which is based on a hybrid model that consists of Landau fluid bulk plasma and drift kinetic EE. Specifically, the bulk plasma kinetic effects such as finite Larmor radius, diamagnetic drifts and Landau dampings, and the EE adiabatic fluid response of convection and non-adiabatic kinetic response of precessional drift resonance are incorporated in the simulations. The global eigenmode equation is solved for e-BAE mode structure and linear dispersion relation in tokamak non-perturbatively. The radial width of e-BAE mode structure becomes narrower as the toroidal mode number increases, which can be explained by the change of Alfvén continuous spectra that interact with kinetic Alfvén waves for corresponding eigenmode formation. The e-BAE growth rate exhibits a non-monotonic variation with toroidal mode number for precessional drift resonance destabilization, while the e-BAE real frequency is close to the continuum accumulation point that almost remains the same. The parametric dependence of e-BAE stability on EE density and that on temperature are analyzed by MAS non-perturbative simulations, which shows that the EE density can affect e-BAE real frequency and thus changes the resonance condition, resulting in e-BAE stabilization in the strong EE drive regime. Further, the EE non-perturbative effect on the symmetry breaking of e-BAE mode structure is reported. The poloidal symmetry breaking characterized by the ‘boomerang’ shape two-dimensional (2D) structure can be greatly enhanced by increasing EE temperature, together with the large radial variation of the poloidal phase angle of dominant principal poloidal harmonic. The radial symmetry breaking of e-BAE mode structure arises when EE density/temperature drive is not symmetric with respect to corresponding rational surface, which can lead to a net volume-averaged value of e-BAE parallel wave number which drives plasma intrinsic rotation. These results are helpful in understanding the e-BAE dynamics observed in recent experiments.
{"title":"Global simulations of energetic electron excitation of beta-induced Alfven eigenmodes","authors":"None Bao Jian, None Zhang Wenlu, None Li Ding","doi":"10.7498/aps.72.20230794","DOIUrl":"https://doi.org/10.7498/aps.72.20230794","url":null,"abstract":"The energetic electron (EE) excitation of beta-induced Alfvén eigenmodes is investigated by using the newly developed global eigenvalue code MAS, which is based on a hybrid model that consists of Landau fluid bulk plasma and drift kinetic EE. Specifically, the bulk plasma kinetic effects such as finite Larmor radius, diamagnetic drifts and Landau dampings, and the EE adiabatic fluid response of convection and non-adiabatic kinetic response of precessional drift resonance are incorporated in the simulations. The global eigenmode equation is solved for e-BAE mode structure and linear dispersion relation in tokamak non-perturbatively. The radial width of e-BAE mode structure becomes narrower as the toroidal mode number increases, which can be explained by the change of Alfvén continuous spectra that interact with kinetic Alfvén waves for corresponding eigenmode formation. The e-BAE growth rate exhibits a non-monotonic variation with toroidal mode number for precessional drift resonance destabilization, while the e-BAE real frequency is close to the continuum accumulation point that almost remains the same. The parametric dependence of e-BAE stability on EE density and that on temperature are analyzed by MAS non-perturbative simulations, which shows that the EE density can affect e-BAE real frequency and thus changes the resonance condition, resulting in e-BAE stabilization in the strong EE drive regime. Further, the EE non-perturbative effect on the symmetry breaking of e-BAE mode structure is reported. The poloidal symmetry breaking characterized by the ‘boomerang’ shape two-dimensional (2D) structure can be greatly enhanced by increasing EE temperature, together with the large radial variation of the poloidal phase angle of dominant principal poloidal harmonic. The radial symmetry breaking of e-BAE mode structure arises when EE density/temperature drive is not symmetric with respect to corresponding rational surface, which can lead to a net volume-averaged value of e-BAE parallel wave number which drives plasma intrinsic rotation. These results are helpful in understanding the e-BAE dynamics observed in recent experiments.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136259597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Xiao Yi-Yao, None He Jia-Hao, None Chen Nan-Kun, None Wang Chao, None Song Ning-Ning
With the rapid updating and development of electronic equipment, electromagnetic interference and electromagnetic radiation pollution have became serious problems, because that excessive electromagnetic interference will not only affect normal operation of electronic equipment but also cause great harm to human health. In general, an ideal material for microwave absorption with the characteristics of high reflection loss (RL) intensity, wide effective absorption band (EAB), thin thickness, and lightweight could effectively consume electromagnetic wave (EMW) energy. Therefore, it is crucial to search for such an ideal microwave absorption material to deal with the electromagnetic radiation pollution. Two-dimensional (2D) carbon/nitride MXene has received more and more attention in recent years, because excellent electrical conductivity and rich surface-functional groups in MXene show positive effects on electromagnetic wave absorption. However, as a non-magnetic material with only dielectric loss, MXene exists obvious impedance mismatch, which greatly limits its practical applications. Combining MXene with magnetic materials becomes a hotspot for exploration of ideal microwave absorption materials. As a typical ferrite, Fe3O4 shows excellent soft magnetic properties such as high saturation magnetization, high chemical stability, simple preparation, and so on. In this paper, the 2D Fe3O4@Ti3C2Tx composite was successfully prepared by hydrothermal method and simple electrostatic adsorption process. Fe3O4 nanoparticles were uniformly anchored on the surface of large-sized monolayer Ti3C2Tx, which effectively reduced the stacking of MXene. By regulating the proportion of magnetic materials, the microwave absorption performance of 2D Fe3O4@Ti3C2Tx composite was investigated. With increasing the content of Fe3O4 nanoparticles in the 2D Fe3O4@Ti3C2Tx composite from 4 mg to 8 mg, the microwave absorption performance was enhanced obviously. This is caused by the abundant Fe3O4/Ti3C2Tx interfaces, scattering channels, point defect, charge density difference in 2D Fe3O4@Ti3C2Tx composite, and the optimized impedance matching. The minimum reflection loss (RLmin) of 2D Fe3O4@Ti3C2Tx composite reached -69.31 dB with the frequency of 16.19 GHz, and the effective absorption band (EAB) achieved 3.39 GHz. With further increasing the content of Fe3O4 nanoparticles to 10 mg, the microwave absorption performance showed a decreasing trend. Excessive Fe3O4 nanoparticles in the 2D Fe3O
{"title":"Enhanced microwave absorption properties of large-sized monolayer two-dimensional Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> loaded with Fe<sub>3</sub>O<sub>4</sub> nanoparticles","authors":"None Xiao Yi-Yao, None He Jia-Hao, None Chen Nan-Kun, None Wang Chao, None Song Ning-Ning","doi":"10.7498/aps.72.20231200","DOIUrl":"https://doi.org/10.7498/aps.72.20231200","url":null,"abstract":"With the rapid updating and development of electronic equipment, electromagnetic interference and electromagnetic radiation pollution have became serious problems, because that excessive electromagnetic interference will not only affect normal operation of electronic equipment but also cause great harm to human health. In general, an ideal material for microwave absorption with the characteristics of high reflection loss (RL) intensity, wide effective absorption band (EAB), thin thickness, and lightweight could effectively consume electromagnetic wave (EMW) energy. Therefore, it is crucial to search for such an ideal microwave absorption material to deal with the electromagnetic radiation pollution. Two-dimensional (2D) carbon/nitride MXene has received more and more attention in recent years, because excellent electrical conductivity and rich surface-functional groups in MXene show positive effects on electromagnetic wave absorption. However, as a non-magnetic material with only dielectric loss, MXene exists obvious impedance mismatch, which greatly limits its practical applications. Combining MXene with magnetic materials becomes a hotspot for exploration of ideal microwave absorption materials. As a typical ferrite, Fe<sub>3</sub>O<sub>4</sub> shows excellent soft magnetic properties such as high saturation magnetization, high chemical stability, simple preparation, and so on. In this paper, the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> composite was successfully prepared by hydrothermal method and simple electrostatic adsorption process. Fe<sub>3</sub>O<sub>4</sub> nanoparticles were uniformly anchored on the surface of large-sized monolayer Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub>, which effectively reduced the stacking of MXene. By regulating the proportion of magnetic materials, the microwave absorption performance of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> composite was investigated. With increasing the content of Fe<sub>3</sub>O<sub>4</sub> nanoparticles in the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> composite from 4 mg to 8 mg, the microwave absorption performance was enhanced obviously. This is caused by the abundant Fe<sub>3</sub>O<sub>4</sub>/Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> interfaces, scattering channels, point defect, charge density difference in 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> composite, and the optimized impedance matching. The minimum reflection loss (RL<sub>min</sub>) of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> composite reached -69.31 dB with the frequency of 16.19 GHz, and the effective absorption band (EAB) achieved 3.39 GHz. With further increasing the content of Fe<sub>3</sub>O<sub>4</sub> nanoparticles to 10 mg, the microwave absorption performance showed a decreasing trend. Excessive Fe<sub>3</sub>O<sub>4</sub> nanoparticles in the 2D Fe<sub>3</sub>O","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134967719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Hall effect refers to the generation of a voltage in a direction perpendicular to the applied current. Since its discovery in 1879, the Hall effect family has become a huge group, and its in-depth study is an important topic in the field of condensed matter physics. The newly discovered nonlinear Hall effect is a new member of the Hall effects. Unlike most of the previous Hall effects, the nonlinear Hall effect does not need to break the time-reversal symmetry of the system but requires the spatial inversion asymmetry. Since 2015, the nonlinear Hall effect has been predicted and confirmed to exist in several kinds of materials with nonuniform distribution of Berry curvature of the energy bands. Experimentally, when a longitudinal ac electric field is applied, a transvers Hall voltage will be generated, with its amplitude proportional to the square of the driving current. Such nonlinear Hall signal contains two components: one is an ac transverse voltage that oscillates at a frequency that twice of the driving current, and the other is a DC signal converted from the injected current. Although the history of the nonlinear Hall effect is only a few years, its broad application prospects in the fields of wireless communication, energy harvesting, and infrared detectors have been widely recognized. The main reason is that the frequency doubling and rectification of electrical signals via the nonlinear Hall effect are achieved by the inherent quantum properties of the material - the Berry curvature dipole moment, and therefore do not have the thermal voltage thresholds and/or the transition time characteristic of semiconductor junctions/diodes. Unfortunately, the existence of the Berry curvature dipole moment has more stringent requirements on the lattice symmetry of the system in addition to the space inversion breaking, and the available materials are very limited. This greatly reduces the chance to optimize the signal of the nonlinear Hall effect and limits the application and development of the nonlinear Hall effect. The rapid development of van der Waals stacking technology in recent years provides a new way to design, tailor and control the symmetry of lattice, and prepare artificial moiré crystals with certain physical properties. Recently, both theoretical and experimental studies on graphene superlattices and transition metal chalcogenide superlattices have shown that artificial moiré superlattice materials can have larger Berry curvature dipole moments than natural non-moiré crystals, which has obvious advantages in generating and manipulating the nonlinear Hall effect. On the other hand, abundant strong correlation effects have been observed in two dimensional superlattices. The study of the nonlinear Hall effect in two-dimensional moiré superlattices can not only give people a new understanding of the momentum space distribution of Berry curvatures, contributing to the realization of more stable topological transport, correlation insula
{"title":"The nonlinear Hall effect in two dimensional moiré superlattices","authors":"None Zefei Wu, None Meizhen Huang, None Ning Wang","doi":"10.7498/aps.72.20231324","DOIUrl":"https://doi.org/10.7498/aps.72.20231324","url":null,"abstract":"The Hall effect refers to the generation of a voltage in a direction perpendicular to the applied current. Since its discovery in 1879, the Hall effect family has become a huge group, and its in-depth study is an important topic in the field of condensed matter physics. The newly discovered nonlinear Hall effect is a new member of the Hall effects. Unlike most of the previous Hall effects, the nonlinear Hall effect does not need to break the time-reversal symmetry of the system but requires the spatial inversion asymmetry. Since 2015, the nonlinear Hall effect has been predicted and confirmed to exist in several kinds of materials with nonuniform distribution of Berry curvature of the energy bands. Experimentally, when a longitudinal ac electric field is applied, a transvers Hall voltage will be generated, with its amplitude proportional to the square of the driving current. Such nonlinear Hall signal contains two components: one is an ac transverse voltage that oscillates at a frequency that twice of the driving current, and the other is a DC signal converted from the injected current. Although the history of the nonlinear Hall effect is only a few years, its broad application prospects in the fields of wireless communication, energy harvesting, and infrared detectors have been widely recognized. The main reason is that the frequency doubling and rectification of electrical signals via the nonlinear Hall effect are achieved by the inherent quantum properties of the material - the Berry curvature dipole moment, and therefore do not have the thermal voltage thresholds and/or the transition time characteristic of semiconductor junctions/diodes. Unfortunately, the existence of the Berry curvature dipole moment has more stringent requirements on the lattice symmetry of the system in addition to the space inversion breaking, and the available materials are very limited. This greatly reduces the chance to optimize the signal of the nonlinear Hall effect and limits the application and development of the nonlinear Hall effect. The rapid development of van der Waals stacking technology in recent years provides a new way to design, tailor and control the symmetry of lattice, and prepare artificial moiré crystals with certain physical properties. Recently, both theoretical and experimental studies on graphene superlattices and transition metal chalcogenide superlattices have shown that artificial moiré superlattice materials can have larger Berry curvature dipole moments than natural non-moiré crystals, which has obvious advantages in generating and manipulating the nonlinear Hall effect. On the other hand, abundant strong correlation effects have been observed in two dimensional superlattices. The study of the nonlinear Hall effect in two-dimensional moiré superlattices can not only give people a new understanding of the momentum space distribution of Berry curvatures, contributing to the realization of more stable topological transport, correlation insula","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135104183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Li Hui-Ling, None Huang Yu-Meng, None Yang Cheng-Yu
In this paper, we focus on discussing the influence of thin disk accretion and asymptotically safe (AS) gravity correction parameter on the shadow and photon ring of black holes. For the thin disk accretion, the dark region is the shadow of the black hole, and the bright photon ring is composed of Direct image, lensing ring and Photon ring. For the specific intensity of the radiation source of the accretion disk, we consider three different emission profile models. For the second-order attenuation function model in which emission starts from the innermost circular orbit, Direct image, lensing ring and Photon ring can be clearly distinguished. The Direct image contributes most of the brightness, and the lensing ring contributes a small portion, while the contribution of the Photon ring can almost be ignored. And the peak value of the corresponding observed intensity decreases with the increase of the AS gravity parameter, that is, the corresponding brightness of the photon ring darkens as correction parameter increases. For the third-order attenuation function model in which the emission begins at the radius of the photon sphere, lensing ring and Photon ring are superimposed on the direct radiation. Thus a new extreme value of the observed intensity emerges, and the extreme value increases with the increase of the AS gravity parameter, which leads to observed photon ring brighter. For the anti-trigonometric attenuation function model in which the radiation starts from the event horizon, the superposition range of lensing ring and Photon ring on the direct radiation becomes larger, which makes photon ring wider. The smaller the AS gravity parameter is, the more difficult it is to distinguish the lensing ring and Photon ring, and the photon ring gets brighter. In short, the results show that the shadow radius decreases with the increase of the AS correction parameter. For different AS gravity correction parameters, the light intensity of emission source, especially emission profiles of the observed intensity are significantly different, resulting in obvious differences for the shadow and bright photon ring of the black hole.
{"title":"Shadow and photon ring of black hole in asymptotically safe gravity","authors":"None Li Hui-Ling, None Huang Yu-Meng, None Yang Cheng-Yu","doi":"10.7498/aps.73.20231233","DOIUrl":"https://doi.org/10.7498/aps.73.20231233","url":null,"abstract":"In this paper, we focus on discussing the influence of thin disk accretion and asymptotically safe (AS) gravity correction parameter on the shadow and photon ring of black holes. For the thin disk accretion, the dark region is the shadow of the black hole, and the bright photon ring is composed of Direct image, lensing ring and Photon ring. For the specific intensity of the radiation source of the accretion disk, we consider three different emission profile models. For the second-order attenuation function model in which emission starts from the innermost circular orbit, Direct image, lensing ring and Photon ring can be clearly distinguished. The Direct image contributes most of the brightness, and the lensing ring contributes a small portion, while the contribution of the Photon ring can almost be ignored. And the peak value of the corresponding observed intensity decreases with the increase of the AS gravity parameter, that is, the corresponding brightness of the photon ring darkens as correction parameter increases. For the third-order attenuation function model in which the emission begins at the radius of the photon sphere, lensing ring and Photon ring are superimposed on the direct radiation. Thus a new extreme value of the observed intensity emerges, and the extreme value increases with the increase of the AS gravity parameter, which leads to observed photon ring brighter. For the anti-trigonometric attenuation function model in which the radiation starts from the event horizon, the superposition range of lensing ring and Photon ring on the direct radiation becomes larger, which makes photon ring wider. The smaller the AS gravity parameter is, the more difficult it is to distinguish the lensing ring and Photon ring, and the photon ring gets brighter. In short, the results show that the shadow radius decreases with the increase of the AS correction parameter. For different AS gravity correction parameters, the light intensity of emission source, especially emission profiles of the observed intensity are significantly different, resulting in obvious differences for the shadow and bright photon ring of the black hole.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136052496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Novel quantum materials such as topological materials, two-dimensional materials, create new opportunities for the spintronic devices. These materials can improve the charge-spin conversion efficiency, provide high-quality interface, and enhance the energy efficiently for spintronic devices. In addition,they have rich interactions and coupling effects, which provides a perfect platform to find new physics and novel methods to control the spintronic properties. Many inspiring results have been reported regarding the research on topological materials and two-dimensional materials, especially the layered topological and two-dimensional magnetic materials, and their heterostructures. This review will discuss recent achievements with these novel quantum materials on spintronic applications, firstly introduce the breakthroughs that topological materials have been made in spin-orbit torque devices, then present two-dimensional magnetic materials and their performance in spintronic devices, finally discuss the research progress in topological materials/two-dimensional magnetic materials heterostructures. This review can help to get a comprehensive understanding of the development of these novel quantum materials in the field of spintronics and inspire new research ideas with these novel materials.
{"title":"Spintronic devices based on topological and two-dimensional materials","authors":"None Longxing Jiang, None Qingchao Li, None Xu Zhang, None Jingfeng Li, None Jing Zhang, None Zuxin Chen, None Min Zeng, None Hao Wu","doi":"10.7498/aps.73.20231166","DOIUrl":"https://doi.org/10.7498/aps.73.20231166","url":null,"abstract":"Novel quantum materials such as topological materials, two-dimensional materials, create new opportunities for the spintronic devices. These materials can improve the charge-spin conversion efficiency, provide high-quality interface, and enhance the energy efficiently for spintronic devices. In addition,they have rich interactions and coupling effects, which provides a perfect platform to find new physics and novel methods to control the spintronic properties. Many inspiring results have been reported regarding the research on topological materials and two-dimensional materials, especially the layered topological and two-dimensional magnetic materials, and their heterostructures. This review will discuss recent achievements with these novel quantum materials on spintronic applications, firstly introduce the breakthroughs that topological materials have been made in spin-orbit torque devices, then present two-dimensional magnetic materials and their performance in spintronic devices, finally discuss the research progress in topological materials/two-dimensional magnetic materials heterostructures. This review can help to get a comprehensive understanding of the development of these novel quantum materials in the field of spintronics and inspire new research ideas with these novel materials.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136054184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Yang Xi-fei, None Shang Lei, None Zou Lin-er, None Shen Yun
The stimulated Brillouin scattering (SBS) effect has the advantage of narrow spectral line width, frequency stability, and sensitivity to gain direction, which is commonly used in the field of integrated photonic devices, such as lasers, slow light generation and microwave photonic filters. In practical applications, due to the low gain coefficient of SBS in traditional chalcogenide waveguides, there are high threshold of pumping power and long waveguide length. In this paper, a inverted-ridge waveguide structure with air slot is designed by adopting As2S3 and SiO2 materials, which presents high backward stimulated Brillouin scattering (BSBS) gain coefficient. This chalcogenide inverted-ridge optical waveguide with air slot can better confine the optical and acoustic fields within the ridge region for improving the coupling efficiency between optical and acoustic fields. More significantly, adding an air slot in the ridge region of this chalcogenide waveguide will produce powerful radiation pressure at the boundary between the air slot and As2S3. Owing to the fact that the acoustic field is mainly distributed near the air slot in the ridge region, the coupling effect of the radiation pressure and acoustic field is significantly enhanced, leading to a significant increase in BSBS gain coefficient. In this paper, the optical fundamental mode as optical mode due to the chalcogenide waveguide with submicron size structure and the six lowest order acoustic modes that meet the matching vector conditions as acoustic mode are calculated, and it is found that the fifth order acoustic mode achieves the maximum BSBS gain coefficient among the six acoustic modes. On this basis, by scanning the waveguide structural parameters of the air slot width, waveguide ridge width & height, and waveguide thickness, the BSBS gain coefficient is as high as 8.22×104 W-1·m-1, which is more than three times the currently reported chalcogenide waveguide with non-suspended structure. Additionally, the calculation results also indicate that this chalcogenide waveguide with a smaller effective mode field area has a higher BSBS gain coefficient in the same optical and acoustic mode, providing a new idea for further improving the BSBS gain coefficient in the design of waveguide structures. At the same time, the impact of optical loss on BSBS gain is also analyzed, and it is found that when the waveguide length exceeds the optimal value, the lost energy caused by the optical loss will be beyond the input energy of the pump optical wave, causing the power of the stokes optical wave to begin to decrease; However, the improvement of the power of pump optical wave not only increases the maximum power of the stokes optical wave, but also rises the optimal value of the waveguide length; The results of simulation calculation have shown that when the input power of pump optical wave is about 20 mW,
{"title":"Study on backward stimulated Brillouin scattering of chalcogenide inverted-ridge optical waveguide with air slot","authors":"None Yang Xi-fei, None Shang Lei, None Zou Lin-er, None Shen Yun","doi":"10.7498/aps.73.20231272","DOIUrl":"https://doi.org/10.7498/aps.73.20231272","url":null,"abstract":"The stimulated Brillouin scattering (SBS) effect has the advantage of narrow spectral line width, frequency stability, and sensitivity to gain direction, which is commonly used in the field of integrated photonic devices, such as lasers, slow light generation and microwave photonic filters. In practical applications, due to the low gain coefficient of SBS in traditional chalcogenide waveguides, there are high threshold of pumping power and long waveguide length. In this paper, a inverted-ridge waveguide structure with air slot is designed by adopting As<sub>2</sub>S<sub>3</sub> and SiO<sub>2</sub> materials, which presents high backward stimulated Brillouin scattering (BSBS) gain coefficient. This chalcogenide inverted-ridge optical waveguide with air slot can better confine the optical and acoustic fields within the ridge region for improving the coupling efficiency between optical and acoustic fields. More significantly, adding an air slot in the ridge region of this chalcogenide waveguide will produce powerful radiation pressure at the boundary between the air slot and As<sub>2</sub>S<sub>3</sub>. Owing to the fact that the acoustic field is mainly distributed near the air slot in the ridge region, the coupling effect of the radiation pressure and acoustic field is significantly enhanced, leading to a significant increase in BSBS gain coefficient. In this paper, the optical fundamental mode as optical mode due to the chalcogenide waveguide with submicron size structure and the six lowest order acoustic modes that meet the matching vector conditions as acoustic mode are calculated, and it is found that the fifth order acoustic mode achieves the maximum BSBS gain coefficient among the six acoustic modes. On this basis, by scanning the waveguide structural parameters of the air slot width, waveguide ridge width & height, and waveguide thickness, the BSBS gain coefficient is as high as 8.22×10<sup>4</sup> W<sup>-1</sup>·m<sup>-1</sup>, which is more than three times the currently reported chalcogenide waveguide with non-suspended structure. Additionally, the calculation results also indicate that this chalcogenide waveguide with a smaller effective mode field area has a higher BSBS gain coefficient in the same optical and acoustic mode, providing a new idea for further improving the BSBS gain coefficient in the design of waveguide structures. At the same time, the impact of optical loss on BSBS gain is also analyzed, and it is found that when the waveguide length exceeds the optimal value, the lost energy caused by the optical loss will be beyond the input energy of the pump optical wave, causing the power of the stokes optical wave to begin to decrease; However, the improvement of the power of pump optical wave not only increases the maximum power of the stokes optical wave, but also rises the optimal value of the waveguide length; The results of simulation calculation have shown that when the input power of pump optical wave is about 20 mW, ","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136054191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Preface to the special topic: The 90 th Anniversary of South China Normal University and Physical Science","authors":"","doi":"10.7498/aps.72.200101","DOIUrl":"https://doi.org/10.7498/aps.72.200101","url":null,"abstract":"","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135156104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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