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}
Zheng Li, Tian Wenlong, Ma Junyi, Yu Yang, Xu Xiao-Dong, Han Hainian, Wei Zhiyi, Zhu Jiangfeng
Femtosecond lasers with GHz repetition rate play an important role in scientific and industrial applications, such as spectroscopy, optical frequency combs and GHz-Burst pulse trains for micro-machining in the ablation-cooled regime. Kerr-lens Mode-locked (KLM) technique and passively modelocking based on Semiconductor Saturable Absorber Mirror (SESAM) are the primary methods to generate GHz femtosecond all-solid-state lasers (ASSLs). Kerr-lens mode-locked Ti:Sapphire lasers have made a significant progress benefitting from the high-power green pump lasers, repetition rate up to 10 GHz has been obtained with an average power of 1.2 W. In the early 21st century, ytterbium ion (Yb3+) doped laser crystals and ceramics with emission wavelengths near 1 μm gained attention due to their high conversion efficiency and broad gain-bandwidth. Combining with the customized SESAM and high-power multimode fiber-coupled laser diodes (LD), GHz Yb-doped ASSLs with watt-level average power may be easily attained and have made rapid progress. However, GHz KLM lasers have strict requirements for the cavity design and pump sources. For satisfying mode matching and enhancing the soft aperture effect within the gain medium, a high-brightness pump source with excellent beam quality (M2~1) is desired, such as the single-mode fiber coupled LD, however, the maximum pump power of which is only~1 W. As a result, the average power of GHz KLM femtosecond lasers is typically restricted to few tens of milliwatts, which limits the further applications. In this work, we reported the first GHz high-power KLM Yb:CaYAlO4 laser by using a high-power single-mode fiber laser instead of the low-power single-mode fiber coupled LDs as the pump source. On the basis of ABCD matrices, a simple four-mirror bow-tie ring cavity was built such that the laser mode can match well with the focused pump spot in the crystal. At the pump power of 8 W, stable unidirectional KLM was achieved, the laser had an average power of 2.1 W with a pulse duration of 88 fs and a repetition rate of 1.8 GHz, corresponding to a peak power of 11.57 kW. The high peak power and extremely short pulse duration are crucial for coherent octave-spanning supercontinuum generation. The powerful GHz KLM laser with sub-100 fs pulse duration provides an attractive source for optical frequency combs and micro-machining applications.
{"title":"Sub-100 fs Kerr-lens Mode-locked femtosecond Yb:CaYAlO4 Laser at GHz repetition rate","authors":"Zheng Li, Tian Wenlong, Ma Junyi, Yu Yang, Xu Xiao-Dong, Han Hainian, Wei Zhiyi, Zhu Jiangfeng","doi":"10.7498/aps.72.20222297","DOIUrl":"https://doi.org/10.7498/aps.72.20222297","url":null,"abstract":"Femtosecond lasers with GHz repetition rate play an important role in scientific and industrial applications, such as spectroscopy, optical frequency combs and GHz-Burst pulse trains for micro-machining in the ablation-cooled regime. Kerr-lens Mode-locked (KLM) technique and passively modelocking based on Semiconductor Saturable Absorber Mirror (SESAM) are the primary methods to generate GHz femtosecond all-solid-state lasers (ASSLs). Kerr-lens mode-locked Ti:Sapphire lasers have made a significant progress benefitting from the high-power green pump lasers, repetition rate up to 10 GHz has been obtained with an average power of 1.2 W. In the early 21st century, ytterbium ion (Yb3+) doped laser crystals and ceramics with emission wavelengths near 1 μm gained attention due to their high conversion efficiency and broad gain-bandwidth. Combining with the customized SESAM and high-power multimode fiber-coupled laser diodes (LD), GHz Yb-doped ASSLs with watt-level average power may be easily attained and have made rapid progress. However, GHz KLM lasers have strict requirements for the cavity design and pump sources. For satisfying mode matching and enhancing the soft aperture effect within the gain medium, a high-brightness pump source with excellent beam quality (M2~1) is desired, such as the single-mode fiber coupled LD, however, the maximum pump power of which is only~1 W. As a result, the average power of GHz KLM femtosecond lasers is typically restricted to few tens of milliwatts, which limits the further applications. In this work, we reported the first GHz high-power KLM Yb:CaYAlO4 laser by using a high-power single-mode fiber laser instead of the low-power single-mode fiber coupled LDs as the pump source. On the basis of ABCD matrices, a simple four-mirror bow-tie ring cavity was built such that the laser mode can match well with the focused pump spot in the crystal. At the pump power of 8 W, stable unidirectional KLM was achieved, the laser had an average power of 2.1 W with a pulse duration of 88 fs and a repetition rate of 1.8 GHz, corresponding to a peak power of 11.57 kW. The high peak power and extremely short pulse duration are crucial for coherent octave-spanning supercontinuum generation. The powerful GHz KLM laser with sub-100 fs pulse duration provides an attractive source for optical frequency combs and micro-machining applications.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"27 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75540133","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}
Han Yan-Rui, Li Wei, Zang Yan-hua, Yang Chang-gang, Chen Rui-Yun, Zhang Guo-Feng, Qin Cheng-Bing, Hu Jian-Yong, Xiao Lian-Tuan
With the rapid development of radio frequency technology such as radar, electronic warfare and 5G communication, the measurement and real-time spectrum characterization of broadband radio frequency signals become increasingly important. The traditional Radio frequency signal real-time measurement technology is limited by the sampling rate of analog-todigital converter and the digital signal processing ability, and has the problems of narrow measurement band, large data volume, and susceptibility to electromagnetic interference. This paper proposes a Radio frequency signal measurement technology based on quantum compression sensing, which uses integrated electro-optical crystal as Radio frequency sensor, and constructs a compression sensing machine by modulating the photon wave function of the measured Radio frequency signal to realize the compression measurement of broadband Radio frequency signal,significantly improving the spectrum sensing bandwidth. The experiment demonstrated the long-term spectrum monitoring of power frequency and intermediate frequency high voltage signals, and the real-time spectrum measurement of high frequency Radio frequency signals. Under the Fourier limit spectrum resolution, the real-time spectrum analysis bandwidth of GHz magnitude is realized, and the data compression rate reaches 1.7×10-5, which can meet the needs of 5G wireless communication, cognitive radio and other applications for broadband Radio frequency signal spectrum measurement, and provide a new technical path for the development of next-generation broadband spectrum sensing technology.
{"title":"Broadband Radio Frequency signal measurement based on quantum compression sensing","authors":"Han Yan-Rui, Li Wei, Zang Yan-hua, Yang Chang-gang, Chen Rui-Yun, Zhang Guo-Feng, Qin Cheng-Bing, Hu Jian-Yong, Xiao Lian-Tuan","doi":"10.7498/aps.72.20230398","DOIUrl":"https://doi.org/10.7498/aps.72.20230398","url":null,"abstract":"With the rapid development of radio frequency technology such as radar, electronic warfare and 5G communication, the measurement and real-time spectrum characterization of broadband radio frequency signals become increasingly important. The traditional Radio frequency signal real-time measurement technology is limited by the sampling rate of analog-todigital converter and the digital signal processing ability, and has the problems of narrow measurement band, large data volume, and susceptibility to electromagnetic interference. This paper proposes a Radio frequency signal measurement technology based on quantum compression sensing, which uses integrated electro-optical crystal as Radio frequency sensor, and constructs a compression sensing machine by modulating the photon wave function of the measured Radio frequency signal to realize the compression measurement of broadband Radio frequency signal,significantly improving the spectrum sensing bandwidth. The experiment demonstrated the long-term spectrum monitoring of power frequency and intermediate frequency high voltage signals, and the real-time spectrum measurement of high frequency Radio frequency signals. Under the Fourier limit spectrum resolution, the real-time spectrum analysis bandwidth of GHz magnitude is realized, and the data compression rate reaches 1.7×10-5, which can meet the needs of 5G wireless communication, cognitive radio and other applications for broadband Radio frequency signal spectrum measurement, and provide a new technical path for the development of next-generation broadband spectrum sensing technology.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"5 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79819699","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}
Liu Yi-Jun, Chen Yi-Wei, Zhu Yu-Jian, Huang Yan, An Dong-Dong, Li Qing-Xin, Gan Qi-Kang, Zhu Wang, Song Jun-Wei, Wang Kai-Yuan, Wei Ling-Nan, Zong Qi-Jun, Liu Shuo-Han, Li Shi-Wei, Liu Zhi, Zhang Qi, Xu Ying-Hai, Cao Xin-Yu, Yang Ao, Wang Hao-Lin, Yang Bing, Andy Shen, Yu Ge-Liang, Wang Lei
Flat band with nearly zero dispersion can be engineered by twisting van der Waals materials relative to each other, and lead to a series of strongly correlated states, for example unconventional superconductivity, correlated insulating state, orbital magnetism. The bandwidth and topological property of electronic band structure in twisted double bilayer graphene is tunable by an external displacement field. This system could be an excellent quantum simulator to study the interplay between topological phase transition and strong electron correlation. Theoretical calculation shows that the broken of C2x symmetry in TDBG by an electric displacement field leads to finite Chern numbers at the lowest conduction and valence band near charge neutrality. Hence Chern insulator may emergent from this topological non-trivial flat band under strong electron interaction. Here, we observe Chern insulator state with Chern number 4 at filling factor v=1 under small magnetic fields on twisted double bilayer graphene with twist angle 1.48°. Moreover, the longitudinal resistance shows a peak under a parallel magnetic field and increases temperature and field, that is analogous to the Pomeranchuk effect in 3He. This phenomenon indicates that Chern insulator at v=1 may originate from isospin polarization.
{"title":"Isospin polarized Chern insulator state of C=4 in twisted double bilayer graphene","authors":"Liu Yi-Jun, Chen Yi-Wei, Zhu Yu-Jian, Huang Yan, An Dong-Dong, Li Qing-Xin, Gan Qi-Kang, Zhu Wang, Song Jun-Wei, Wang Kai-Yuan, Wei Ling-Nan, Zong Qi-Jun, Liu Shuo-Han, Li Shi-Wei, Liu Zhi, Zhang Qi, Xu Ying-Hai, Cao Xin-Yu, Yang Ao, Wang Hao-Lin, Yang Bing, Andy Shen, Yu Ge-Liang, Wang Lei","doi":"10.7498/aps.72.20230497","DOIUrl":"https://doi.org/10.7498/aps.72.20230497","url":null,"abstract":"Flat band with nearly zero dispersion can be engineered by twisting van der Waals materials relative to each other, and lead to a series of strongly correlated states, for example unconventional superconductivity, correlated insulating state, orbital magnetism. The bandwidth and topological property of electronic band structure in twisted double bilayer graphene is tunable by an external displacement field. This system could be an excellent quantum simulator to study the interplay between topological phase transition and strong electron correlation. Theoretical calculation shows that the broken of C2x symmetry in TDBG by an electric displacement field leads to finite Chern numbers at the lowest conduction and valence band near charge neutrality. Hence Chern insulator may emergent from this topological non-trivial flat band under strong electron interaction. Here, we observe Chern insulator state with Chern number 4 at filling factor v=1 under small magnetic fields on twisted double bilayer graphene with twist angle 1.48°. Moreover, the longitudinal resistance shows a peak under a parallel magnetic field and increases temperature and field, that is analogous to the Pomeranchuk effect in 3He. This phenomenon indicates that Chern insulator at v=1 may originate from isospin polarization.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"17 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79879134","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 study of integrable systems is one of important topics both in physics and in mathematics. However, traditional studies on integrable systems are usually restricted in (1+1)-and (2+1)-dimensions. The main reasons come from the fact that high-dimensional integrable systems are extremely rare. Recently, we found that a large number of high dimensional integrable systems can be derived from low dimensional ones by means of a deformation algorithm. In this paper, the (1+1)-dimensional Kaup-Newell (KN) system is extended to a (4+1)-dimensional system with help of the deformation algorithm. In addition to the original (1+1)-dimensional KN system, the new system also contains three reciprocal forms of the (1+1)-dimensional KN system. The model also contains a large number of new (D+1)-dimensional (D ≤ 3) integrable systems. The Lax integrability and symmetry integrability of the (4+1)-dimensional KN system are also proved. It is very difficult to solve the new high-dimensional KN systems. In this paper, we only investigate the traveling wave solutions of a (2+1)-dimensional reciprocal derivative nonlinear Schrödinger equation. The general envelope travelling wave can expressed by a complicated elliptic integral. The single envelope dark (gray) soliton of the derivative nonlinear Schodinger equation can be implicitly written.
{"title":"Higher dimensional reciprocal integrable Kaup-Newell systems","authors":"Lou S Y, Hao Xia-Zhi, Jia Man","doi":"10.7498/aps.72.20222418","DOIUrl":"https://doi.org/10.7498/aps.72.20222418","url":null,"abstract":"The study of integrable systems is one of important topics both in physics and in mathematics. However, traditional studies on integrable systems are usually restricted in (1+1)-and (2+1)-dimensions. The main reasons come from the fact that high-dimensional integrable systems are extremely rare. Recently, we found that a large number of high dimensional integrable systems can be derived from low dimensional ones by means of a deformation algorithm. In this paper, the (1+1)-dimensional Kaup-Newell (KN) system is extended to a (4+1)-dimensional system with help of the deformation algorithm. In addition to the original (1+1)-dimensional KN system, the new system also contains three reciprocal forms of the (1+1)-dimensional KN system. The model also contains a large number of new (D+1)-dimensional (D ≤ 3) integrable systems. The Lax integrability and symmetry integrability of the (4+1)-dimensional KN system are also proved. It is very difficult to solve the new high-dimensional KN systems. In this paper, we only investigate the traveling wave solutions of a (2+1)-dimensional reciprocal derivative nonlinear Schrödinger equation. The general envelope travelling wave can expressed by a complicated elliptic integral. The single envelope dark (gray) soliton of the derivative nonlinear Schodinger equation can be implicitly written.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"70 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79934752","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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