Li De-Zhang, Lu Zhi-Wei, Zhao Yu-Jun, Yang Xiao-Bao
The stochastic dynamics of spin semiclassical system at finite temperature is usually described by stochastic Landau-Lifshitz equation. In this work, the stochastic differential equation for spin semiclassical system is studied. The generalized formulation of effective Langevin equation and the corresponding Fokker-Planck equation are derived. The obtained effective Langevin equation offers an accurate description of the distribution in the canonical ensemble for spin semiclassical system. When the damping term and the stochastic term vanish, the effective Langevin equation reduces to the semiclassical equation of motion for spin system. Hence, the effective Langevin equation can be seen as a generalization of the stochastic Landau-Lifshitz equation. The explicit expressions for the effective Langevin equation and the corresponding Fokker-Planck equation are shown in both Cartesian and Spherical coordinates. It is demonstrated that, the longitudinal effect can be easily illustrated from the expressions in Spherical coordinates. The effective Langevin equation is applied to the simple system of a single spin in a constant magnetic field. In choosing an appropriate form, the Langevin equation can be easily solved and the stationary Boltzmann distribution can be obtained. The correctness of the Langevin approach to the spin semiclassical system is thus confirmed.
{"title":"Study of the generalization of spin semiclassical Langevin equation","authors":"Li De-Zhang, Lu Zhi-Wei, Zhao Yu-Jun, Yang Xiao-Bao","doi":"10.7498/aps.72.20230106","DOIUrl":"https://doi.org/10.7498/aps.72.20230106","url":null,"abstract":"The stochastic dynamics of spin semiclassical system at finite temperature is usually described by stochastic Landau-Lifshitz equation. In this work, the stochastic differential equation for spin semiclassical system is studied. The generalized formulation of effective Langevin equation and the corresponding Fokker-Planck equation are derived. The obtained effective Langevin equation offers an accurate description of the distribution in the canonical ensemble for spin semiclassical system. When the damping term and the stochastic term vanish, the effective Langevin equation reduces to the semiclassical equation of motion for spin system. Hence, the effective Langevin equation can be seen as a generalization of the stochastic Landau-Lifshitz equation. The explicit expressions for the effective Langevin equation and the corresponding Fokker-Planck equation are shown in both Cartesian and Spherical coordinates. It is demonstrated that, the longitudinal effect can be easily illustrated from the expressions in Spherical coordinates. The effective Langevin equation is applied to the simple system of a single spin in a constant magnetic field. In choosing an appropriate form, the Langevin equation can be easily solved and the stationary Boltzmann distribution can be obtained. The correctness of the Langevin approach to the spin semiclassical system is thus confirmed.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"22 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81501989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shuai Han, Qiubo Guo, Yaxiang Lu, Liquan Chen, Yong-Sheng Hu
Aqueous alkali-metal-ion batteries are a popular frontier research area, expected to apply for large-scale energy storage due to their high safety, low cost, and environmental friendliness. Depending on diversified social development, batteries ought to function in various ambient, including polar regions and high-altitude locales. Delivering excellent electrochemical performance at low temperatures is crucial to develop aqueous alkali-metal-ion batteries. This review summarizes the representative research progress in the field of aqueous low-temperature alkali-metal-ion batteries in recent years,based on the subjects of electrolyte, electrode, and interface. Firstly, we discussed the challenges of aqueous alkali-metal-ion batteries operated at low temperatures and the corresponding failure mechanisms. At subzero temperatures, aqueous alkali-metal-ion batteries couldn't work or exhibit little capacity, arising from the frozen electrolytes, electrode materials with slow kinetics, and huge interface impedances, which seriously limits their wide application in low-temperature conditions. Then, combined with the latest research work, various strategies have been investigated to improve the electrochemical performance of batteries at low temperatures. To date, the strategies for reducing the freezing point of electrolytes have primarily focused on breaking H-bonds between free water molecules by increasing salt concentration, adding organic/inorganic additives, and using hydrogel as electrolytes. In terms of electrodes, the related studies have concentrated on regulating the structure and morphology of electrodes, introducing the dual ion battery mechanism, and using organic materials and Zn electrodes to alleviate the slow ion dynamics of electrodes. In addition, adding appropriate organic solvents that can generate protective layers with low interface impedance on the electrode surface in the electrolyte can also improve the low-temperature performance of aqueous alkali-metal-ion batteries. Finally, we evaluated multi-dimensionally all strategies, expected to provide a comprehensive reference and point out the direction for the further improvement and practical application of the aqueous alkali-metal-ion batteries at low temperatures.
{"title":"Recent Progress in Aqueous Alkali-metal-ion batteries at low temperatures","authors":"Shuai Han, Qiubo Guo, Yaxiang Lu, Liquan Chen, Yong-Sheng Hu","doi":"10.7498/aps.72.20230024","DOIUrl":"https://doi.org/10.7498/aps.72.20230024","url":null,"abstract":"Aqueous alkali-metal-ion batteries are a popular frontier research area, expected to apply for large-scale energy storage due to their high safety, low cost, and environmental friendliness. Depending on diversified social development, batteries ought to function in various ambient, including polar regions and high-altitude locales. Delivering excellent electrochemical performance at low temperatures is crucial to develop aqueous alkali-metal-ion batteries. This review summarizes the representative research progress in the field of aqueous low-temperature alkali-metal-ion batteries in recent years,based on the subjects of electrolyte, electrode, and interface. Firstly, we discussed the challenges of aqueous alkali-metal-ion batteries operated at low temperatures and the corresponding failure mechanisms. At subzero temperatures, aqueous alkali-metal-ion batteries couldn't work or exhibit little capacity, arising from the frozen electrolytes, electrode materials with slow kinetics, and huge interface impedances, which seriously limits their wide application in low-temperature conditions. Then, combined with the latest research work, various strategies have been investigated to improve the electrochemical performance of batteries at low temperatures. To date, the strategies for reducing the freezing point of electrolytes have primarily focused on breaking H-bonds between free water molecules by increasing salt concentration, adding organic/inorganic additives, and using hydrogel as electrolytes. In terms of electrodes, the related studies have concentrated on regulating the structure and morphology of electrodes, introducing the dual ion battery mechanism, and using organic materials and Zn electrodes to alleviate the slow ion dynamics of electrodes. In addition, adding appropriate organic solvents that can generate protective layers with low interface impedance on the electrode surface in the electrolyte can also improve the low-temperature performance of aqueous alkali-metal-ion batteries. Finally, we evaluated multi-dimensionally all strategies, expected to provide a comprehensive reference and point out the direction for the further improvement and practical application of the aqueous alkali-metal-ion batteries at low temperatures.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"13 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81723624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reservoir computing (RC) is a simplified recurrent neural network, can be implemented by using a nonlinear system with delay feedback, called as delay-based RC. Various nonlinear nodes and feedback loop structures are proposed. Most works are based on the dynamical responses in intensity of the nonlinear systems. There are also a photoelectric RC system based on wavelength dynamics and an all-optical RC based on the phase dynamics of a semiconductor laser with optical feedback, as well as so-called polarization dynamics of a vertical cavity surface emitting laser (VCSEL). However, these VCSEL-RCs actually are based on the intensity dynamics of two mutually orthogonal polarization modes, or polarization-resolved intensity dynamics. The RC based on rich dynamical responses in polarization has not yet been seen. A semiconductor optical amplifier (SOA) fiber ring laser can produce rich dynamical states in polarization, is used in optical chaotic secure communication and distributed optical fiber sensing. To further expand the application of polarization dynamics of the SOA fiber ring laser and open up a new direction for the research of optical RC neural network, an all-optical RC system based on polarization dynamics of the ring laser is proposed. The ring laser is used as the reservoir, and the SOA as the nonlinear node. After the input signal is masked according to a synchronization scheme, it is injected into the reservoir by intensity modulation for a continuous wave generated by a super-luminescent light emitting diode (SLED). The dynamical response in polarization of the ring laser is detected by a polarizer and a photodetector. The influences of the SOA operation current, output power of the SLED and attenuation of a variable optical attenuator (VOA) in the fiber loop on the polarization dynamic characteristic, mainly refers to the output degree of polarization, of the laser are analyzed experimentally. The fading memory abilities and nonlinear responses of the RC system based on the polarization dynamic response and intensity dynamic response are compared in experiment. The influences of output power of the SLED and attenuation of the VOA on fading memory ability, consistency and separation of the RC system based on the two kinds of dynamic responses are investigated experimentally. Thus the range of the VOA attenuation is determined. The network performance of the polarization dynamics RC system is evaluated by processing the Santa Fe time series prediction task and the multi-waveform recognition task. The prediction error can be as low as 0.0058 for the time series prediction task, and the accuracy can be as high as 100% for the recognition task under the appropriate system parameters and only 30 virtual nodes. The experimental results show that the polarization dynamics RC system has good prediction performance and classification ability, which are comparable to the existing intensity dynamics RC system based on the ring laser. The system
{"title":"All-optical reservoir computing system based on polarization dynamics","authors":"Fang Nian, Qian Ruolan, Wang Shuai","doi":"10.7498/aps.72.20230722","DOIUrl":"https://doi.org/10.7498/aps.72.20230722","url":null,"abstract":"Reservoir computing (RC) is a simplified recurrent neural network, can be implemented by using a nonlinear system with delay feedback, called as delay-based RC. Various nonlinear nodes and feedback loop structures are proposed. Most works are based on the dynamical responses in intensity of the nonlinear systems. There are also a photoelectric RC system based on wavelength dynamics and an all-optical RC based on the phase dynamics of a semiconductor laser with optical feedback, as well as so-called polarization dynamics of a vertical cavity surface emitting laser (VCSEL). However, these VCSEL-RCs actually are based on the intensity dynamics of two mutually orthogonal polarization modes, or polarization-resolved intensity dynamics. The RC based on rich dynamical responses in polarization has not yet been seen. A semiconductor optical amplifier (SOA) fiber ring laser can produce rich dynamical states in polarization, is used in optical chaotic secure communication and distributed optical fiber sensing. To further expand the application of polarization dynamics of the SOA fiber ring laser and open up a new direction for the research of optical RC neural network, an all-optical RC system based on polarization dynamics of the ring laser is proposed. The ring laser is used as the reservoir, and the SOA as the nonlinear node. After the input signal is masked according to a synchronization scheme, it is injected into the reservoir by intensity modulation for a continuous wave generated by a super-luminescent light emitting diode (SLED). The dynamical response in polarization of the ring laser is detected by a polarizer and a photodetector. The influences of the SOA operation current, output power of the SLED and attenuation of a variable optical attenuator (VOA) in the fiber loop on the polarization dynamic characteristic, mainly refers to the output degree of polarization, of the laser are analyzed experimentally. The fading memory abilities and nonlinear responses of the RC system based on the polarization dynamic response and intensity dynamic response are compared in experiment. The influences of output power of the SLED and attenuation of the VOA on fading memory ability, consistency and separation of the RC system based on the two kinds of dynamic responses are investigated experimentally. Thus the range of the VOA attenuation is determined. The network performance of the polarization dynamics RC system is evaluated by processing the Santa Fe time series prediction task and the multi-waveform recognition task. The prediction error can be as low as 0.0058 for the time series prediction task, and the accuracy can be as high as 100% for the recognition task under the appropriate system parameters and only 30 virtual nodes. The experimental results show that the polarization dynamics RC system has good prediction performance and classification ability, which are comparable to the existing intensity dynamics RC system based on the ring laser. The system","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"23 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85187686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dirac quantum materials comprise a broad category of condensed matter systems characterized by low-energy excitations described by the Dirac equation. These excitations, which can manifest as either collective states or band structure effects, have been identified in a wide range of systems, from exotic quantum fluids to crystalline materials. Over the past several decades, they have sparked extensive experimental and theoretical investigations in various materials, such as topological insulators and topological semimetals. The study of Dirac quantum materials has also opened up new possibilities for topological quantum computing, giving rise to a burgeoning field of physics and offering a novel platform for realizing rich topological phases, including various quantum Hall effects and topological superconducting phases. Furthermore, the topologically non-trivial band structures of Dirac quantum materials give rise to plentiful intriguing transport phenomena, including longitudinal negative magnetoresistance, quantum interference effects, and helical magnetic effects, among others. Currently, numerous transport phenomena in Dirac quantum materials remain poorly understood from a theoretical standpoint, such as linear magnetoresistance in weak fields, anomalous Hall effects in nonmagnetic materials, and three-dimensional quantum Hall effects. Investigating these transport properties will not only deepen our understanding of Dirac quantum materials but also provide crucial insights for their potential applications in spintronics and quantum computing. This review provides a comprehensive overview of the quantum transport theory and quantum anomaly effects related to the Dirac equation, with a focus on massive Dirac fermions and quantum anomalous semimetals. Additionally, it offers insights into the realization of parity anomaly and half-quantized quantum Hall effects in semi-magnetic topological insulators. Lastly, the review discusses the key scientific questions of interest in the field of quantum transport theory.
{"title":"Recent progress of transport theory in Dirac quantum materials","authors":"Wang Huan-Wen, Fu Bo, Shen Shun-Qing","doi":"10.7498/aps.72.20230672","DOIUrl":"https://doi.org/10.7498/aps.72.20230672","url":null,"abstract":"Dirac quantum materials comprise a broad category of condensed matter systems characterized by low-energy excitations described by the Dirac equation. These excitations, which can manifest as either collective states or band structure effects, have been identified in a wide range of systems, from exotic quantum fluids to crystalline materials. Over the past several decades, they have sparked extensive experimental and theoretical investigations in various materials, such as topological insulators and topological semimetals. The study of Dirac quantum materials has also opened up new possibilities for topological quantum computing, giving rise to a burgeoning field of physics and offering a novel platform for realizing rich topological phases, including various quantum Hall effects and topological superconducting phases. Furthermore, the topologically non-trivial band structures of Dirac quantum materials give rise to plentiful intriguing transport phenomena, including longitudinal negative magnetoresistance, quantum interference effects, and helical magnetic effects, among others. Currently, numerous transport phenomena in Dirac quantum materials remain poorly understood from a theoretical standpoint, such as linear magnetoresistance in weak fields, anomalous Hall effects in nonmagnetic materials, and three-dimensional quantum Hall effects. Investigating these transport properties will not only deepen our understanding of Dirac quantum materials but also provide crucial insights for their potential applications in spintronics and quantum computing. This review provides a comprehensive overview of the quantum transport theory and quantum anomaly effects related to the Dirac equation, with a focus on massive Dirac fermions and quantum anomalous semimetals. Additionally, it offers insights into the realization of parity anomaly and half-quantized quantum Hall effects in semi-magnetic topological insulators. Lastly, the review discusses the key scientific questions of interest in the field of quantum transport theory.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"64 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85208264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The band gap is a key physical quantity in material design. First-principles calculations based on density functional theory can approximately predict the band gap, which often require significant computational resources and time. Deep learning models have the advantages of good fitting ability and automatic feature extraction from the data, and are gradually being applied to predict the band gap. In this paper, aiming at the problem of quickly obtaining the band gap value of perovskite materials, a feature fusion neural network model named CGCrabNet is established, and the transfer learning strategy is used to predict the band gap of perovskite materials. CGCrabNet extracts features from both chemical equation and crystal structure of materials, and fits the mapping between features and band gaps. It is an end-to-end neural network model. Based on the pre-training data obtained from the Open Quantum Materials Database (OQMD dataset), the CGCrabNet parameters can be fine-tuned by using only 175 perovskite material data to improve the robustness of the model.The numerical experimental results show that the prediction error of the CGCrabNet model for band gap prediciton based on the OQMD dataset is 0.014eV, which is lower than that obtained from the prediction based on Compositionally restricted attention-based network (CrabNet). The mean absolute error of the model developed in this paper for the prediction of perovskite materials is 0.374eV, which is lower 0.304eV, 0.441eV and 0.194eV than that obtained from random forest regression, support vector machine regression and gradient boosting regression, respectively. The mean absolute error of the test set of CGCrabNet trained only using perovskite data is 0.536 eV, and the mean absolute error of the pre-trained CGCrabNet has decreased by 0.162 eV, which indicates that the transfer learning strategy has significant role in improving the prediction accuracy of small data sets (perovskite material data sets). The difference between the predicted band gap of some perovskite materials such as SrHfO3and RbPaO3 by the model and the band gap calculated by first-principles is less than 0.05eV, which indicates that the CGCrabNet can quickly and accurately predict the properties of new materials and accelerate the development process of new materials.
{"title":"Band gap prediction of perovskite materials based on transfer learning","authors":"Sun Tao, Yuan Jian-Mei","doi":"10.7498/aps.72.20231027","DOIUrl":"https://doi.org/10.7498/aps.72.20231027","url":null,"abstract":"The band gap is a key physical quantity in material design. First-principles calculations based on density functional theory can approximately predict the band gap, which often require significant computational resources and time. Deep learning models have the advantages of good fitting ability and automatic feature extraction from the data, and are gradually being applied to predict the band gap. In this paper, aiming at the problem of quickly obtaining the band gap value of perovskite materials, a feature fusion neural network model named CGCrabNet is established, and the transfer learning strategy is used to predict the band gap of perovskite materials. CGCrabNet extracts features from both chemical equation and crystal structure of materials, and fits the mapping between features and band gaps. It is an end-to-end neural network model. Based on the pre-training data obtained from the Open Quantum Materials Database (OQMD dataset), the CGCrabNet parameters can be fine-tuned by using only 175 perovskite material data to improve the robustness of the model.The numerical experimental results show that the prediction error of the CGCrabNet model for band gap prediciton based on the OQMD dataset is 0.014eV, which is lower than that obtained from the prediction based on Compositionally restricted attention-based network (CrabNet). The mean absolute error of the model developed in this paper for the prediction of perovskite materials is 0.374eV, which is lower 0.304eV, 0.441eV and 0.194eV than that obtained from random forest regression, support vector machine regression and gradient boosting regression, respectively. The mean absolute error of the test set of CGCrabNet trained only using perovskite data is 0.536 eV, and the mean absolute error of the pre-trained CGCrabNet has decreased by 0.162 eV, which indicates that the transfer learning strategy has significant role in improving the prediction accuracy of small data sets (perovskite material data sets). The difference between the predicted band gap of some perovskite materials such as SrHfO3and RbPaO3 by the model and the band gap calculated by first-principles is less than 0.05eV, which indicates that the CGCrabNet can quickly and accurately predict the properties of new materials and accelerate the development process of new materials.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"37 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85316877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mixing between shell material and gas fuel, caused by hydrodynamic instability, isolated defects, or kinetic effects, is the key to understand the degradation of implosion performance in the research of inertial confinement fusion. Understanding the mixing mechanism and reducing its impact is of extreme importance to achieve the ignition and high gain. The impact of mixing morphology on thermonuclear reaction rate in sub grid level has gradually attracted people’s attention in recent years due to its direct influence on burn rate and fusion process, the study on physical model of thermonuclear reaction rate in different mix morphology has important scientific significance and application value.In the paper, the dependence of thermonuclear reaction rate on mass distribution of different fuel concentrations at sub grid scale is derived. Based on thermodynamic equilibrium and ideal gas equation of state, the physical law of the evolution of the thermonuclear reaction rate with mix morphology under the dominance of diffusion mixing is revealed through analytical formula and numerical solution of diffusion equation in one-dimensional spherical geometry. It is convinced that the mixing amount directly affects the thermonuclear reaction rate by mainly affecting the volume fraction of the fuel, and the mixing diffusion time determined by heterogeneous mixing scale and diffusion coefficient directly affects the evolution behavior of the thermonuclear reaction rate. Furthermore, based on mutual diffusion coefficient obtained from direct simulation of diffusion process by Monte Carlo method, the difference of impact to thermonuclear reaction rate for low-Z Carbon and high-Z gold mixing is quantitatively investigated. Heterogeneous mix size with 0.1μm, 0.01μm respectively for the low-Z and high-Z mixing can be treated as atomic mix in burn rate aspect, and heterogeneous mix size with 10μm, 1μm respectively for the low-Z and high-Z mixing can be treated as ideal chunk mix in burn rate aspect, and heterogeneous mix size in the middle state needs to be evaluated by using the heterogeneous mixing model of thermonuclear reaction rate in the paper. Finally, the physical model is compared with 3D simulation results of the heterogeneous mixing effect experiment called "MARBLE Campaign" carried out on OMEGA laser facility, which is designed as a separated reactant experiments and capsules are filled with deuterated foam and HT gas pores of different size, covering typical mix morphology from atomic mix to chunk mix, which validate the reliability of the theoretical evaluation about the evolution of mixing morphology and its impact to thermonuclear reaction rate.This work is significant for the design and improvement of inertial confinement fusion mixing effect experiment in China.
{"title":"Investigation on the fusion reaction rate of deuterium and tritium under heterogeneous mixing","authors":"Shen Gang, Zhong Bin, Wu Yong, Wang Jian-guo","doi":"10.7498/aps.72.20221197","DOIUrl":"https://doi.org/10.7498/aps.72.20221197","url":null,"abstract":"Mixing between shell material and gas fuel, caused by hydrodynamic instability, isolated defects, or kinetic effects, is the key to understand the degradation of implosion performance in the research of inertial confinement fusion. Understanding the mixing mechanism and reducing its impact is of extreme importance to achieve the ignition and high gain. The impact of mixing morphology on thermonuclear reaction rate in sub grid level has gradually attracted people’s attention in recent years due to its direct influence on burn rate and fusion process, the study on physical model of thermonuclear reaction rate in different mix morphology has important scientific significance and application value.In the paper, the dependence of thermonuclear reaction rate on mass distribution of different fuel concentrations at sub grid scale is derived. Based on thermodynamic equilibrium and ideal gas equation of state, the physical law of the evolution of the thermonuclear reaction rate with mix morphology under the dominance of diffusion mixing is revealed through analytical formula and numerical solution of diffusion equation in one-dimensional spherical geometry. It is convinced that the mixing amount directly affects the thermonuclear reaction rate by mainly affecting the volume fraction of the fuel, and the mixing diffusion time determined by heterogeneous mixing scale and diffusion coefficient directly affects the evolution behavior of the thermonuclear reaction rate. Furthermore, based on mutual diffusion coefficient obtained from direct simulation of diffusion process by Monte Carlo method, the difference of impact to thermonuclear reaction rate for low-Z Carbon and high-Z gold mixing is quantitatively investigated. Heterogeneous mix size with 0.1μm, 0.01μm respectively for the low-Z and high-Z mixing can be treated as atomic mix in burn rate aspect, and heterogeneous mix size with 10μm, 1μm respectively for the low-Z and high-Z mixing can be treated as ideal chunk mix in burn rate aspect, and heterogeneous mix size in the middle state needs to be evaluated by using the heterogeneous mixing model of thermonuclear reaction rate in the paper. Finally, the physical model is compared with 3D simulation results of the heterogeneous mixing effect experiment called \"MARBLE Campaign\" carried out on OMEGA laser facility, which is designed as a separated reactant experiments and capsules are filled with deuterated foam and HT gas pores of different size, covering typical mix morphology from atomic mix to chunk mix, which validate the reliability of the theoretical evaluation about the evolution of mixing morphology and its impact to thermonuclear reaction rate.This work is significant for the design and improvement of inertial confinement fusion mixing effect experiment in China.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"158 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85421579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hong Hao-Yi, Gao Mei-Qi, Gui Long-Cheng, Hua Jun, Liang Jian, Shi Jun, Zou Jin-Tao
Understanding the statistical fluctuations of lattice observables over the gauge configurations is important both theoretically and practically. It provides physical insights to tackle the famous signal-to-noise problem and the sign problem, and inspires new thoughts in developing methodologies to improve the signal of lattice calculations. Among many efforts, exploring the connections between the real and imaginary parts of lattice numerical results is a novel way to learn about the lattice signal and error, since both the real and imaginary parts originate from the same sampling of gauge fields and their distributions over the gauge samples are in principle related. Specifically, by analyzing the distributions of the real and imaginary parts of quenched lattice two-point functions with high statistics and non-zero momentum, this work proposes a possible quantitative formula connecting these two distributions as R(x) = ∫dyS(y - x) [I(y)K(Uy)], where R(x) stands for the real-part distribution, I(x) the imaginary-part distribution, S(x) the underlying signal distribution and K(Ux) a kernel function of the gauge field. This theoretical assumption is of general validity since the kernel function contains the gauge field information that determines all the distributions. The formula is numerically verified by calculating the non-trivial statistical correlations of the real parts and the kernel-function-modified imaginary parts with further assumptions on the kernel function. It is found that the most naïve guess of K(Ux) = 1 does not work, which leads to no statistically significant correlation. Meanwhile, the assumption that K(Ux) is only a sign function works well, giving rise to ~ 70% correlation. Then, random distortions on the absolute values of the imaginary parts are added with different strength and the results show that even a small distortion, say 1%, would reduce the correlation between the real and imaginary parts down to less than 50%. This essentially proves that the observed ~ 70% correlation is highly non-trivial and the hypothesis of K(Ux) being a sign function captures at least some of the physical mechanisms behind the scenes. Employing this correlation, the variance of lattice results can be improved by around 40%. It is not a significant improvement in practice; however, this study offers an innovative strategy to understand the source of statistical uncertainties in lattice QCD and to improve the signal-to-noise ratios in lattice calculations. Further studies utilizing the power of machine learning on a variety of more precise lattice data will hopefully give better indication and constraint on the form of the kernel function.
{"title":"The Imaginary-Part Distribution of Lattice QCD Data and Signal Improvement","authors":"Hong Hao-Yi, Gao Mei-Qi, Gui Long-Cheng, Hua Jun, Liang Jian, Shi Jun, Zou Jin-Tao","doi":"10.7498/aps.72.20230869","DOIUrl":"https://doi.org/10.7498/aps.72.20230869","url":null,"abstract":"Understanding the statistical fluctuations of lattice observables over the gauge configurations is important both theoretically and practically. It provides physical insights to tackle the famous signal-to-noise problem and the sign problem, and inspires new thoughts in developing methodologies to improve the signal of lattice calculations. Among many efforts, exploring the connections between the real and imaginary parts of lattice numerical results is a novel way to learn about the lattice signal and error, since both the real and imaginary parts originate from the same sampling of gauge fields and their distributions over the gauge samples are in principle related. Specifically, by analyzing the distributions of the real and imaginary parts of quenched lattice two-point functions with high statistics and non-zero momentum, this work proposes a possible quantitative formula connecting these two distributions as R(x) = ∫dyS(y - x) [I(y)K(Uy)], where R(x) stands for the real-part distribution, I(x) the imaginary-part distribution, S(x) the underlying signal distribution and K(Ux) a kernel function of the gauge field. This theoretical assumption is of general validity since the kernel function contains the gauge field information that determines all the distributions. The formula is numerically verified by calculating the non-trivial statistical correlations of the real parts and the kernel-function-modified imaginary parts with further assumptions on the kernel function. It is found that the most naïve guess of K(Ux) = 1 does not work, which leads to no statistically significant correlation. Meanwhile, the assumption that K(Ux) is only a sign function works well, giving rise to ~ 70% correlation. Then, random distortions on the absolute values of the imaginary parts are added with different strength and the results show that even a small distortion, say 1%, would reduce the correlation between the real and imaginary parts down to less than 50%. This essentially proves that the observed ~ 70% correlation is highly non-trivial and the hypothesis of K(Ux) being a sign function captures at least some of the physical mechanisms behind the scenes. Employing this correlation, the variance of lattice results can be improved by around 40%. It is not a significant improvement in practice; however, this study offers an innovative strategy to understand the source of statistical uncertainties in lattice QCD and to improve the signal-to-noise ratios in lattice calculations. Further studies utilizing the power of machine learning on a variety of more precise lattice data will hopefully give better indication and constraint on the form of the kernel function.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"8 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85466007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhang Zhen-Chi, Tang Hui-Bo, Wang Jin-Chan, Si Hua-Chong, Wang Zhi, Lan Xiang, Hu Guang-Yue
Diamagnetic cavity and flute instability generated by plasma expansion in an external magnetic field are important phenomena in space and fusion physics.We use a nanosecond laser to irradiate a carbon planar target to generate plasma, and at the same time apply a 7T transverse pulsed strong magnetic field to the plasma. The flute instability generated on the surface of the diamagnetic cavity when the plasma expands in an external magnetic field is studied experimentally. Data analysis shows that under our experimental parameters, the radius of gyration of electrons(ρe) is much smaller than the density gradient scale length of the diamagnetic cavity(Ln), while the ion's gyration radius(ρi) is much larger than Ln, indicating that the electrons are magnetized while the ions are non magnetized. The relative drift between electrons and ions provides free energy for the development of instability.The drift velocity is composed of the gravity drift velocity and the diamagnetic gradient drift velocity. The calculation shows that the gravity drift velocity is much larger than the diamagnetic gradient drift velocity in our experiment, so the instability belongs to the Large Larmor Radius Instability. By filling the target chamber with helium, we found that the background gas can significantly inhibit the development of flute instability. When the background gas pressure exceeds 50Pa (about 1% of the interface plasma density), the flute instability is almost is completely suppressed. Kinetic dispersion equations show that ion-ion collisions and electron-ion collision effects are the main factors that inhibit the development of instability. Calculations on the dispersion equation show that ion-ion collisions are the main factor that inhibits the development of instabilities.
{"title":"Influence of ambient gas to flute instability produced at the interface between laser plasma and external magnetic field","authors":"Zhang Zhen-Chi, Tang Hui-Bo, Wang Jin-Chan, Si Hua-Chong, Wang Zhi, Lan Xiang, Hu Guang-Yue","doi":"10.7498/aps.72.20231108","DOIUrl":"https://doi.org/10.7498/aps.72.20231108","url":null,"abstract":"Diamagnetic cavity and flute instability generated by plasma expansion in an external magnetic field are important phenomena in space and fusion physics.We use a nanosecond laser to irradiate a carbon planar target to generate plasma, and at the same time apply a 7T transverse pulsed strong magnetic field to the plasma. The flute instability generated on the surface of the diamagnetic cavity when the plasma expands in an external magnetic field is studied experimentally. Data analysis shows that under our experimental parameters, the radius of gyration of electrons(ρe) is much smaller than the density gradient scale length of the diamagnetic cavity(Ln), while the ion's gyration radius(ρi) is much larger than Ln, indicating that the electrons are magnetized while the ions are non magnetized. The relative drift between electrons and ions provides free energy for the development of instability.The drift velocity is composed of the gravity drift velocity and the diamagnetic gradient drift velocity. The calculation shows that the gravity drift velocity is much larger than the diamagnetic gradient drift velocity in our experiment, so the instability belongs to the Large Larmor Radius Instability. By filling the target chamber with helium, we found that the background gas can significantly inhibit the development of flute instability. When the background gas pressure exceeds 50Pa (about 1% of the interface plasma density), the flute instability is almost is completely suppressed. Kinetic dispersion equations show that ion-ion collisions and electron-ion collision effects are the main factors that inhibit the development of instability. Calculations on the dispersion equation show that ion-ion collisions are the main factor that inhibits the development of instabilities.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"9 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83440570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiong Pei-Yu, Ni Zhuang, Lin Ze-Feng, Bai Xin-Bo, Liu Tian-Xiang, Zhang Xiang-Yu, Yuan Jie, Wang Xu, Shi Jing, Jin Kui
BaxSr1-xTiO3(BST) ferroelectric thin films are widely used in microwave tunable devices due to their high dielectric constant, strong electric field tunability and low microwave loss. However, because of the temperature dependence of dielectric constant in ferroelectric materials, the high-tunability for conventional single component ferroelectric thin films can only be achieved in the vicinity of Curie Temperature (TC) which results in that the ferroelectric thin films are difficult to apply to wide temperature range. To obtain ferroelectric thin films available for temperature stable functional devices, single composition Ba0.2Sr0.8TiO3 thin films, Ba0.5Sr0.5TiO3 thin films and heterostructure ofBa0.2Sr0.8TiO3/Ba0.5Sr0.5TiO3 thin films are deposited by pulsed laser deposition (PLD). By comparing with their dielectric properties in a wide temperature range, it’s found that the temperature sensitivity of BST films can be effectively reduced by introducing a composition gradient along the epitaxial direction. However, the heterostructure engineering may bring extra troubles caused by interfaces, which may limit the quality factor Q. In this paper, we extend our combinatorial film deposition technique to ferroelectric materials, and successfully fabricated in-plane composition-spread Ba1-xSrxTiO3 thin films, which are expected to broaden the phase transition temperature range of BST films while avoiding the problem of interface control.
{"title":"Composition-spread Epitaxial Ferroelectric Thin Films for Temperature Insensitive Functional Devices","authors":"Xiong Pei-Yu, Ni Zhuang, Lin Ze-Feng, Bai Xin-Bo, Liu Tian-Xiang, Zhang Xiang-Yu, Yuan Jie, Wang Xu, Shi Jing, Jin Kui","doi":"10.7498/aps.72.20230154","DOIUrl":"https://doi.org/10.7498/aps.72.20230154","url":null,"abstract":"Ba<sub>x</sub>Sr<sub>1-x</sub>TiO<sub>3</sub>(BST) ferroelectric thin films are widely used in microwave tunable devices due to their high dielectric constant, strong electric field tunability and low microwave loss. However, because of the temperature dependence of dielectric constant in ferroelectric materials, the high-tunability for conventional single component ferroelectric thin films can only be achieved in the vicinity of Curie Temperature (<i>T</i><sub>C</sub>) which results in that the ferroelectric thin films are difficult to apply to wide temperature range. To obtain ferroelectric thin films available for temperature stable functional devices, single composition Ba<sub>0.2</sub>Sr<sub>0.8</sub>TiO<sub>3</sub> thin films, Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> thin films and heterostructure ofBa<sub>0.2</sub>Sr<sub>0.8</sub>TiO<sub>3</sub>/Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> thin films are deposited by pulsed laser deposition (PLD). By comparing with their dielectric properties in a wide temperature range, it’s found that the temperature sensitivity of BST films can be effectively reduced by introducing a composition gradient along the epitaxial direction. However, the heterostructure engineering may bring extra troubles caused by interfaces, which may limit the quality factor <i>Q</i>. In this paper, we extend our combinatorial film deposition technique to ferroelectric materials, and successfully fabricated in-plane composition-spread Ba<sub>1-<i>x</i></sub>Sr<i><sub>x</sub></i>TiO<sub>3</sub> thin films, which are expected to broaden the phase transition temperature range of BST films while avoiding the problem of interface control.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"54 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85789379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rydberg atom can respond to weak microwave electric field signal in real-time by using its electromagnetically induced transparency effect to realize down conversion of space microwave electric field signal, which can be used as a superheterodyne receiver. The Rydberg atom superheterodyne receiver is a new receiving system composed of Rydberg atoms, photodetectors, and electronic information processing modules. Presently, domestic and foreign scholars have conducted in-depth research on the physical response mechanism of Rydberg atomic superheterodyne receiving technology. However, no complete receiving link analysis model has been established, which is not conducive to optimizing its system performance. Based on the physical mechanism of the Rydberg atom responding to the microwave electric field, this paper introduces the concept of intrinsic expansion coefficient, establishes and experimentally verifies the receiving link model of the Rydberg atom superheterodyne receiver, and briefly discusses the influence of the intrinsic expansion coefficient on the system sensitivity and response characteristics, which provides theoretical guidance for the optimization of the performance of the Rydberg atom superheterodyne receiving system. Last, the Rydberg atomic and the electronic receiving links' sensitivity performance is discussed and compared.
{"title":"Research on Intrinsic Expansion Coefficients in Rydberg Atomic Heterodyne Receiving Link","authors":"Wu Fengchuan, An Qiang, Yao Jiawei, Fu Yunqi","doi":"10.7498/aps.72.20222091","DOIUrl":"https://doi.org/10.7498/aps.72.20222091","url":null,"abstract":"Rydberg atom can respond to weak microwave electric field signal in real-time by using its electromagnetically induced transparency effect to realize down conversion of space microwave electric field signal, which can be used as a superheterodyne receiver. The Rydberg atom superheterodyne receiver is a new receiving system composed of Rydberg atoms, photodetectors, and electronic information processing modules. Presently, domestic and foreign scholars have conducted in-depth research on the physical response mechanism of Rydberg atomic superheterodyne receiving technology. However, no complete receiving link analysis model has been established, which is not conducive to optimizing its system performance. Based on the physical mechanism of the Rydberg atom responding to the microwave electric field, this paper introduces the concept of intrinsic expansion coefficient, establishes and experimentally verifies the receiving link model of the Rydberg atom superheterodyne receiver, and briefly discusses the influence of the intrinsic expansion coefficient on the system sensitivity and response characteristics, which provides theoretical guidance for the optimization of the performance of the Rydberg atom superheterodyne receiving system. Last, the Rydberg atomic and the electronic receiving links' sensitivity performance is discussed and compared.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"2002 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86403057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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