bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of atmosphere attenuation on quantum interferometric radar
Authors: Wang Shu  , Ren Yi-Chong  , Rao Rui-Zhong  , Miao Xi-Kui  ,   Key Laboratory of Atmospheric Composition and Optical Radiation, Anhui Institute of Optics and Fine Mechanics, Chinese Academy Sciences, Hefei 230031, China;,   University of Science and Technology of China, Hefei 230026, China;,   Key Laboratory of Electro-Optical Countermeasures Test and Evaluation Technology, Luoyang 471003, China
Published: December 2020

There has been aroused much interest in quantum metrology such as quantum radar, due to its applications in sub-Raleigh ranging and remote sensing. For quantum radar, the atmospheric absorption and diffraction rapidly degrade any actively transmitted quantum states of light, such as N00N and MM' states. Thus for the high-loss condition, the optimal strategy is to transmit coherent state of light, which can only provide sensitivity at the shot-noise limit but suffer no worse loss than the linear Beer's law for classical radar attenuation.
In this paper, the target detection theory of quantum interferometric radar in the presence of photon loss is thoroughly investigated with the model of Mach-Zehnder interferometer, and the dynamic evolution of the quantum light field in the detecting process is also investigated. We utilize the parity operator to detect the return signal of quantum interferometric radar with coherent-state source. Then we compare the detection result of quantum radar with that of classical radar, which proves that the quantum radar scheme that employs coherent radiation sources and parity operator detection can provide an N-fold super-resolution, which is much below the Rayleigh diffraction limit; besides, the sensitivity of this scheme can also achieve the shot-noise-limit.
Also, we analyze the effect of atmospheric attenuation on the performance of quantum radar, and find that the sensitivity is seriously influenced by atmospheric attenuation:only when the reference beam and the detection beam have the same transmissivity, will the sensitivity increase monotonically with increasing the photon number per pulse N, otherwise it first increases and then decreases with increasing N. Further, the sensivity is directly proportional to 1/N for the first case.
In conclusion, we investigate the effects of atmospheric absorption on the resolution and sensitivity of quantum radar, and find that one can overcome the harmful effects of atmospheric attenuation by adjusting the transmissivity of reference beam to the atmospheric transmittance.
Excited-state dynamics of m-dichlorobezene in ultrashort laser pulses
Authors: Shen Huan  , Hu Chun-Long  , Deng Xu-Lan  ,   College of Science, Huazhong Agricultural University, Wuhan 430070, China;,   Institute of Applied Physics, Huazhong Agricultural University, Wuhan 430070, China;,   State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
Published: December 2020

The excited state dynamics of aromatic hydrocarbon has attracted a great deal of attention due to its important role in photophysics and atmosphere chemistry. With the benefit of ultra-short laser pulses, the ultrafast phenomenon can be studied in a time resolved way. In the present work, m-dichlorobenzene, a typical model of aromatic hydrocarbon, is investigated by the femtosecond time resolved time-of-flight mass spectroscopy. In order to reveal its excited state dynamics, m-dichlorobenzene is pumped to the excited state after absorbing one 200/267 nm photon, and then ionized by absorbing 800 nm photons. Time resolved mass spectra are recorded with time of flight. At 200 nm, m-dichlorobenzene is excited to a (, *) state. Three decay components are observed in the transient profiles of m-dichlorobenzene ions, which correspond to three competition channels in the excited states. The first channel is an ultrafast dissociation process via a repulsive state with (n, *) or (, *) character, and the lifetime is (0.150.01) ps. The second channel is an internal conversion process from the populated excited state to the hot ground state, and the lifetime of the redistribution of the internal vibration in the hot ground state is (4.940.08) ps. The third channel is an intersystem crossing process to the triplet state, and the lifetime is (110.094.33) ps. Moreover, the transient profiles of C6H4Cl+/C6H4+ display similar decay tendencies to the transient profile of parent ion, except that longer lifetime constants ((127.3829.29) ps for C6H4Cl+, and (123.7637.12) ps for C6H4+, respectively) are observed. It is likely that the fragment ions result from the dissociative ionization of the parent molecule. At 267 nm, m-dichlorobenzene is excited to the first excited state with (n, *) character. Only C6H4Cl2+ and C6H4Cl+ are observed in the two-color mass spectrum. A slow decay component (~(1.060.05) ns) is obtained for both the parent ion and the fragment ion. It is attributed to an intersystem crossing process from the first excited state S1 to the triplet state T1. Furthermore, the transient profile of C6H4Cl+ displays other decay components, i.e., (2.480.09) ps, in addition to the slow decay component. This fast decay process can be attributed to an internal conversion process from the populated excited states to the hot ground states. The present study provides a more in-depth understanding of the ultrafast excited state dynamics of m-dichlorobenzene.
Identifying the influence of GaN/InxGa1-xN type last quantum barrier on internal quantum efficiency for III-nitride based light-emitting diode
Authors: Shi Qiang  , Li Lu-Ping  , Zhang Yong-Hui  , Zhang Zi-Hui  , Bi Wen-Gang  ,   School of Electronics and Information Engineering, Hebei University of Technology, Tianjin 300401, China;,   Key Laboratory of Electronic Materials and Devices of Tianjin, Tianjin 300401, China
Published: December 2020

GaN/InxGa1-xN-type last quantum barrier (LQB) proves to be useful for Ⅲ-nitride based light-emitting diode (LED) in enhancing the internal quantum efficiency (IQE) and suppressing the efficiency droop level that often takes place especially when the injection current is high. In this work, GaN/InxGa1-xN-type LQB reported by the scientific community to enhance the IQE is first reviewed and summarized. Then, the influences of indium composition and thickness of the InxGa1-xN layer on the performance of LED incorporated with the GaN/InxGa1-xN-type LQB are studied. Through analyzing energy band diagrams calculated with APSYS, we find that the[0001] oriented LQB features an electron depletion due to the polarization induced negative charges at the GaN/InxGa1-xN interface. The electron depletion enhances the electron blocking effect and reduces the electron accumulation at the InxGa1-xN/AlGaN interface, leading to an improved IQE for the LED. In addition, increasing the indium composition of the InxGa1-xN layer will generate more negative interface charges, which result in further increased conduction band barrier height for the electrons and reduced electron leakage. On the other hand, for the GaN/InxGa1-xN-type LQB with a fixed indium composition, there exists an optimum thickness for the InxGa1-xN layer in maximizing the improvement of IQE for the LED, mainly because the interaction between two mechanisms co-exists when varying the thickness of the InxGa1-xN layer, i.e., the initial increase in the InxGa1-xN layer thickness will lead to an increased conduction band barrier height, which prevents electrons from leaking into the InxGa1-xN layer. However, further increasing the InxGa1-xN layer thickness to a certain value, tunneling effect will kick in as a result of the simultaneously reduced GaN thickness-the electrons will tunnel through the thin GaN layer in the LQB from the quantum wells to the InxGa1-xN layer. This will cause electrons to increase in the InxGa1-xN layer. Therefore, as a result of the interaction between the above-mentioned two mechanisms, there is an optimum thickness for the InxGa1-xN layer such that the electrons in the InxGa1-xN layer will reach a minimal value, which in turn will lead to a maximized conduction band barrier height for the AlGaN electron blocking layer and facilitate the performance of LEDs.
Flaws in classical proofs of vector Kirchhoff integral theorem and its new strict proof
Authors: Huang Xiao-Wei  , Sheng Xin-Qing  ,   Center for Electromagnetic Simulation, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

The vector Kirchhoff integral theorem (VKI) is an important formula in electromagnetic (EM) theory,especially it is a basis of the optical diffraction theory.Recently,it has been found that there exist some flaws in the proofs presented in the literature.There are mainly two types of methods to prove the VKI.The first type of method is to employ the vector analysis to prove the VKI directly.Some flaws of this type of proof presented in the literature have been found and pointed out in this paper.The second type of method is to employ the scalar Kirchhoff Integral (SKI) to directly obtain the VKI. The SKI was first derived by Kirchhoff (1882).In spite of its mathematical inconsistency and its physical deficiencies, the SKI works remarkably well in the optical domain and has been the basis of most of the work on diffraction.However, the proofs for SKI usually need the scalar radiation conditions.The scalar radiation condition was first proposed by Sommerfeld to ensure the uniqueness of the solution of certain exterior boundary value problems in mathematical physics. But whether the scalar radiation conditions were suitable for the EM was not sure.In fact,for electromagnetic field,we have another vector radiation conditions which have been verified to be adaptable for all the radiation and scattering fields.It is difficult to obtain the scalar radiation conditions directly by just separating three Cartesian directions from the vector one,because the different scalar components are coupled together after the rotation and cross product operation.Actually,few strict proofs could be found to support the fact that EM satisfies the scalar radiation condition. So as the supplementary,the scalar radiation conditions will be derived in detail with far-field approximation method in this paper.To avoid using the scalar radiation condition which may bring some non-rigorousness,we perform a new strict proof for the VKI by using the vector analysis identities. The rest of this paper is organized as follows.In Section 2,the different proofs presented in the classical books will be analyzed in detail.The flaws existing in these proofs will be pointed out.After that,in Section 3,based on the Stratton-Chu formula,a new strict proof will be given with using the vector identities.In Section 4,a sensitivity analysis is numerically performed to confirm our demonstration.Finally,the conclusions are drawn from the present study in Section 5.The scalar radiation conditions will be discussed in the appendix.
Mechanism of the motion of spherical microparticle induced by a collapsed microbubble
Authors: Wei Meng-Ju  , Chen Li  , Wu Tao  , Zhang Hong-Yan  , Cui Hai-Hang  ,   School of Environment and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
Published: December 2020

Collapse of a confined bubble is the core problem of bubble dynamics. The recent study has shown that the collapse of macroscopic bubble may drive the motion of suspended particle with the similar size, but, there has still been a lack of the relevant study on a microscale. In the experiment about the bubble driven micro-motor, the locomotion of motor pushed by microjetting has been noticed. However, due to the limitation of experimental conditions, it is difficult to reveal the details of propulsion mechanism. In this paper, the volume of fluid based numerical method is adopted to simulate the interaction process between a collapsing microbubble and the suspended particle nearby. The spatial distribution and the time evolution of flow field are obtained, and the velocity that the micromotor could be achieved is deduced by integrating the impulsive force. The results show that when the bubble size is fixed, the interaction force is inversely proportional to the size of microparticle and the gap between microparticle and bubble. The Kelvin impulse theorem is used to clarify the difference between the interaction on a macroscopic scale and that on a microscopic scale. This study not only extends the scope of cavitation dynamics, which reveals the characteristics of interaction between bubble and particle on a microscale, but also is significant for improving the efficiency of self-propelled micro-motor.
Structural and electronic properties of T-graphene and its derivatives
Authors: Liu Hui-Ying  , Zhang Xiu-Qin  , Fang Yi-Mei  , Zhu Zi-Zhong  ,   College of Science, Jimei University, Xiamen 361021, China;,   Department of Physics, Semiconductor Optoelectronic Material and High Efficiency Conversion Device Collaborative Innovation Center, Xiamen University, Xiamen 361005, China
Published: December 2020

Recent years there has been aroused a growing interest in designing two-dimensional (2D) structures of carbon allotropes, owing to the great success in graphene. The T-graphene is a newly proposed 2D carbon allotrope possessing tetragonal symmetry other than hexagonal symmetry of graphene. Also, the energetic and dynamical stabilities of T-graphene have been revealed. So motivated, we investigate the structural stabilities and electronic properties of T-graphene and especially its derivatives-n(n=1-5) by using the first-principle calculation based on the density function theory. By changing the atomic number (n) of the linear carbon chains connecting the two tetragon rings of T-graphene, a series of sp-sp2 hybrid structures can be formed, which is named T-graphene derivatives-n. The calculation results show that the structural stabilities, chemical bond types and electronic structures of these materials depend greatly on the parity of n. Owing to a strong π-bond formed by eight carbon atoms in T-graphene, it becomes the one with the lowest energy in all these materials studied in this work. An interesting phenomenon is found that the T-graphene derivatives-n with even n are dynamically stable as witnessed by the calculated phonon spectra without imaginary modes, while those with odd n are dynamically unstable. The metallic behaviors are present in the T-graphene derivatives-n with even carbon atoms in the linear carbon chains, showing an alternating single and triple C–C bonds. Besides, we observe that the metallicity of the T-graphene derivatives-n with even n becomes stronger as n increases. On the other hand, the linear carbon chains with odd carbon atoms are comprised of continuous C=C double bonds. These T-graphene derivatives-n with odd n also show metallic behaviors, but turn into magnetic materials (except for n=1), the magnetic moments are about 0.961μB (n=3) and 0.863μB (n=5) respectively, and ferromagnetic ordering is the only possibility for the magnetism, which rarely occurs in carbon material. Our first-principle studies indicate that the introducing carbon chains between the tetragonal carbon rings of T-graphene constitute an efficient method to obtain new two-dimensional carbon allotrope. With different numbers (even or odd) of carbon atoms on the chains, the constructed 2D carbon allotropes could show contrasting dynamical and magnetic properties. These findings provide a theoretical basis for designing two-dimensional carbon materials and carbon-based nanoelectronic devices.
First-principle study of effect of asymmetric biaxial tensile strain on band structure of Germanium
Authors: Dai Zhong-Hua  , Qian Yi-Chen  , Xie Yao-Ping  , Hu Li-Juan  , Li Xiao-Di  , Ma Hai-Tao  ,   Key Laboratory for Microstructures and Institute of Materials, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China
Published: December 2020

The strain engineering is an effective method to modulate the optical properties of germanium. The biaxial tensile strain has been extensively studied, most of the investigations focusing on biaxial tensile strain with equal in-plane strain at different crystal orientations, namely symmetric biaxial tensile strain. However, the effect of biaxial tensile strain with unequal in-plane strain at different crystal orientations, namely asymmetric biaxial tensile strain, has not been reported. In this paper, we systematically investigate the effect of asymmetric biaxial tensile strain on the band structure of Ge by using first-principle calculation.#br#We firstly calculate and analyze the dependence of band gap on strain for Ge with asymmetric biaxial tensile strain along three low Miller index planes, i.e., (001), (101) and (111). Then, we present the values of band gap and strain for some typical indirect-to-direct bandgap-transition-points under asymmetric biaxial tensile strain. Finally, we analyze the influence of biaxial tensile strain on the valance band structure. For the asymmetric biaxial tensile strain along the (001) plane, the indirect-to-direct band gap transition only occurs when the strain of one orientation is larger than 2.95%. For asymmetric biaxial tensile strain along the (101) plane, the indirect-to-direct band gap transition only occurs when the strain of one orientation is larger than 3.44%. Asymmetric biaxial tensile strain along the (111) plane cannot transform Ge into direct band gap material.#br#For asymmetric biaxial tensile strains along the (001) and (101) plane, the indirect-to-direct band gap transition points can be adjusted by changing the combination of in-plane strain at different crystal orientations. The value of bandgap of direct-band-gap Ge under biaxial tensile strain is inversely proportional to the area variation induced by application of strain. The asymmetric biaxial tensile strain along the (001) plane is the most effective to transform Ge into direct band gap material among the three types of biaxial strains, which are similar to the symmetric biaxial tensile strains.#br#In addition, the symmetric biaxial tensile strain will remove the three-fold degenerate states of valance band maximum, leading to a removal of the degeneracy between one heavy hole band and the light hole band. For biaxial tensile strain along the (001) and (101) plane, the asymmetric biaxial tensile strain could further remove the degeneracy between another heavy hole band and the light hole band.
Fragile-to-strong transition in metallic glass-forming liquids
Authors: Hu Li-Na  , Zhao Xi  , Zhang Chun-Zhi  ,   Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Ji'nan 250061, China;,   College of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China
Published: December 2020

It has been observed that many glass-forming liquids are transformed from fragile to strong liquids in a supercooled region upon cooling. This is the so-called fragile-to-strong (F-S) transition. Since its discovery in water, the F-S transition, as a frontier problem, as well as a hot issue, in condensed matter physics and material science, has aroused the considerable interest of researchers. It has been generally accepted that the F-S transition might be a universal dynamic behavior of metallic glass-forming liquid (MGFL). Studying the F-S transition is important not only for better understanding the nature of glass transition, uncovering the microstructural inheritance during the liquid-solid transformation, clarifying the structural competition during crystallization, improving the stability of MGs, but also for promoting the standardization during the production and treatment technology of MGs. In this paper, the general and special features of the F-S transition for bulk and marginal MGFLs are studied and described in terms of a physical model. A characteristic parameter f is introduced to quantify the F-S transition. With two relaxation regimes, on the basis of Mauro-Yuanzheng-Ellison-Gupta-Allan model, we propose a generalized viscosity model for capturing the liquids with the F-S transition. Using this model, we calculate the F-S transition temperature for metallic glass. From the calculation results, the F-S transition might occur around (1.36±0.03) Tg. By using the hyperquenching annealing-calorimetric approach, we find that the anomalous crystallization behavior occurs in both LaAlNi and CuZrAl glass ribbons. This phenomenon implies the existence of a thermodynamic F-S transition, which could be used as an alternative method of detecting the F-S transition in MGFLs. To date, the origin of the F-S transition is far from understanding. We find that the F-S transition in CuZr(Al) GFLs is attributed to the competition among the MRO clusters composed of different locally ordering configurations. By comparing the parameter f with the parameter r that characterizes the competition between the α and the slow β relaxations in 19 MGFLs, we find that the slow β relaxation plays a dominant role in the F-S transition and the extent of the F-S transition is mainly determined by the degree of the comparability in structure units between the α and the slow β relaxations. The existence of the liquid-liquid phase transition might also be the root of the F-S transition. The tendency of investigation of the F-S transition is also evaluated.
Evolution of zero-determinant strategy in iterated snowdrift game
Authors: Wang Jun-Fang  , Guo Jin-Li  , Liu Han  , Shen Ai-Zhong  ,   Business School, University of Shanghai Science and Technology, Shanghai 200093, China;,   School of Mathematics and Statistics, North China University of Water Resources and Electric Power, Zhengzhou 450046, China;,   Trade and Technology Department, Xijing University, Xi'an 710123, China
Published: December 2020

Zero-determinant strategy can set unilaterally or enforce a linear relationship on opponent's income, thereby achieving the purpose of blackmailing the opponent. So one can extort an unfair share from the opponent. Researchers often pay attention to the steady state and use the scores of the steady state in previous work. However, if the player changes his strategy frequently in daily game, the steady state cannot attain easily. It is necessary to attain the transient income if there is a difference in income between the previous state and the steady state. In addition, what will happen if evolutionary player encounters an extortioner? The evolutionary results cannot be proven, just using the simulations in previous work. Firstly, for the iterated game between extortioner and cooperator, we introduce the transient distribution, the transient income, and the arrival time to steady state by using the Markov chain theory. The results show that the extortioner's payoff in the previous state is higher than in the steady state when the extortion factor is small, and the results go into reverse when the extortion factor is large. Furthermore, the larger the extortion factor, the harder the cooperation will be. And the small extortion factor conduces to approaching the steady state earlier. The results provide a method to calculate the dynamic incomes of both sides and give us a time scale of reaching the steady state. Secondly, for the iterated game between extortioner and evolutionary player, we prove that the evolutionary player must evolve into a full cooperation strategy if he and his opponent are both defectors in the initial round. Then, supposing that the evolutionary speed is proportional to the gradient of his payoff, we simulate the evolutionary paths. It can be found that the evolutionary speeds are greatly different in four initial states. In particular, the evolutionary player changes his strategy into cooperation rapidly if he defects in the initial round. He also gradually evolves into a cooperator if he cooperates in the initial round. That is to say, the evolutionary process relates to his initial behavior, but the result is irrelevant to his behavior. It can be concluded that the zero-determinant strategy acts as a catalyst in promoting cooperation. Finally, we prove that the set of zero-determinant strategy and fully cooperation is not a Nash equilibrium.
Design and analysis of high-spectral resolution lidar discriminator
Authors: Di Hui-Ge  , Hua Hang-Bo  , Zhang Jia-Qi  , Zhang Zhan-Fei  , Hua Deng-Xin  , Gao Fei  , Wang Li  , Xin Wen-Hui  , Zhao Heng  ,   School of Mechanical and Precision Instrument Engineering, Xi'an University of Technology, Xi'an 710048, China
Published: December 2020

An accurate aerosol optical property can be obtained by a high spectral resolution lidar (HSRL) technique, which employs a narrow spectral filter to suppress Mie scattering in the lidar return signal. The ability for filter to suppress Rayleigh scattering is critical for the HSRL. In the HSRL system, Rayleigh scattering signal is obtained and aerosol scattering is suppressed at least by a factor of 10-5 through using the narrow filter. Usually, an atomic absorption filter can reach this level. While, the gaseous absorption lines do not exist at many convenient laser wavelengths, thus restricting the development of multi-wavelength HSRL instrument. A new and practical filtering method is proposed to realize the precise detection of atmospheric optical parameters by using the reflection field of Fabry-Perot (FP) interferometer. An optical splitting system with high spectral resolution is designed and its spectral characteristics are analyzed. Based on the characteristic of hyper-spectral lidar detection signal, the variations of spectral separation ratio and Rayleigh signal transmittance with reflectivity and cavity length are discussed. Spectral separation ratio is the transmittance ratio of aerosol scattering signal to molecular scattering signal through the spectral filter. With the increases of FP cavity length and surface reflectivity, the spectral separation ratio decreases and the Rayleigh signal transmission increases. The high spectral separation ratio and Rayleigh signal transmittance can be achieved by the reflection field of FP interferometer when the FP cavity length and reflectivity parameter can be chosen reasonably. We design an FP interferometer with a cavity length of 36 mm and reflectivity of 0.4. Its spectral separation ratio is affected by the echo divergence and incidence angle. The spectral separation ratio keeps unchanged when the beam divergence angle is within 3 mrad and the incident angle of the beam is within 0.5 mrad. In addition, a simulation analysis model is established based on the error propagation. An observed actual Mie-scattering profile is used for analyzing the errors. Moreover, the influences of the divergence angle and the incident angle of the echo beam on detection results are also discussed. The results show that the proposed FP interferometer can achieve fine spectral separation of Mie and Rayleigh scattering signal, and the error of detection result is not sensitive to laser divergence angle. Fine aerosol optical parameters can be achieved when the divergence and incidence angles are controlled within 10 mrad and 1.5 mrad, respectively.
Experimental investigation of tin fragments mixing with gas subjected to laser driven shock
Authors: Xin Jian-Ting  , Zhao Yong-Qiang  , Chu Gen-Bai  , Xi Tao  , Shui Min  , Fan Wei  , He Wei-Hua  , Gu Yu-Qiu  ,   Laboratory of Science and Technology on Plasma Physics, Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

When a shock wave reflects from the free surface of a solid sample, fragments may be emitted from the surface. Understanding the process of the fragments mixing with gas is an important subject for current researches in inertial confinement fusion and high pressure science. Particularly, obtaining the fragments size and distribution is important for developing or validating the physical fragmentation model. At present, the reported quantitative data are less due to the great challenges in the time-resolved measurements of the fragments.#br#Recently, high-power laser has appeared as a promising shock loading means for fragment investigation. The advantages existing in such means mainly include small sample (~μm to mm-order), convenient dynamic diagnosis and soft recovery of fragments. Our group has performed the dynamic fragmentation experiments under laser shock loading metal. The ejected fragments under different loading pressures are softly recovered by low density medium of poly 4-methy1-1-pentene (PMP) foam. The sizes, shapes and penetration depths of the fragments are quantitatively analyzed by X-ray micro-tomography and the improved-watershed method.#br#This paper mainly reports the research advances in the process of the fragments mixing with gas. The laser-driven shock experiments of tin sample are performed at Shenguang-Ⅲ prototype laser facility. Under two typical loading pressures, the fragments mixed with gas (N2) are recovered by PMP foam with a density of 200 mg/cm3, and the pressure of gas is 1 atm. The high resolution reconstructed images of the recovered fragments provided by X-ray micro-tomography and computed tomography reconstruction show that the shapes of the fragments are almost homogeneous, and their sizes are in a range of about 1-20 micron. These images are very different from the images of the fragments recovered in vacuum under similar loading pressures. The observed fragments under loading pressure less than 10 GPa in vacuum are some thin layers, while the loading pressure is increased up to more than 30 GPa, a large number of small spherical particles are observed in the front of the recovery fragments, thin layers in the middle, and these spherical particles have diameters ranging from one dozen to several hundreds of micrometers. The sizes and number of fragments are analyzed by the improved watershed method. The resulting distribution of the fragments mixed with gas follows bilinear exponential distribution. Comprehensive analyses of former simulations and our experimental results show that the secondary fragmentation should occur in the process of the fragments mixing with gas.
Effect of Sr doping on electronic structure of La1-xSrxMnO3/LaAlO3/SrTiO3 heterointerface
Authors: Ruan Lu-Feng  , Wang Lei  , Sun De-Yan  ,   Department of Physics, School of Physics and Material Science, East China Normal University, Shanghai 200241, China
Published: December 2020

In the past decades, the interface between two oxides LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention since a quasi-two-dimensional electron gas (q2DEG) at the interface was observed. It is generally believed that polar discontinuity at polar/non-polar oxide interface is responsible for the emergence of q2DEG at the interface. Recently, how to modulate the q2DEG at the interface is becoming a new research focus. Capping other oxide thin layer on LAO layer is one of alternative approaches to controlling the generation of q2DEG at interface. However the mechanism or origin for tuning q2DEG at capped LAO/STO interface has not yet completely understood. Using the first-principles calculations within the density functional theory, the electronic properties of La1-xSrxMnO3-capped LaAlO3/SrTiO3 heterointerfaces with different doping concentrations of Sr atoms are investigated. The system is composed of four layers of La1-xSrxMnO3 (LSMO), three layers of LAO and four layers of STO, denoted as 4LSMO/3LAO/4STO. The interface is normal to the[001] direction of cubic phase, namely (La1-xSrxO) layer and (MnO2) layer appear alternately at LSMO, and (LaO) layer and (AlO2) layer appear alternately at LAO. In the absence of LSMO layers, q2DEG does not appear at the LAO/STO interface. It is found that the electronic structure of 4LSMO/3LAO/4STO can be tuned significantly by capping LSMO layers. For concentration of doped Sr atoms less than 1/3, a q2DEG at LAO/STO interface is observed. In this case, a strong polarization existing in LSMO, together with the polarization in LAO, forces the electrons to be redistributed, thus inducing the q2DEG at LAO/STO interface. With the increase of the concentration of Sr atoms, the polarization in LSMO becomes weaker and weaker. When the concentration is higher than 1/3, the polaried electric field fails to make the electrons redistributed, thus the q2DEG disappears from interface.#br#Another interesting feature of the present work relates to the distribution of Sr atoms in LSMO. It is found that the electronic structure of 4LSMO/3LAO/4STO changes little with respect to the distribution of Sr atoms in LSMO. The system does not undergo the conductor-to-insulator transition for Sr atoms doping at different sites as long as the concentration of Sr does not change. The reason could be understood as follows. The LSMO layer is in a metallic state, the extra electrons, which are generated due to substituting La with Sr, will be delocalized rather than localized at each doped Sr atom. It is reasonable to expect that the electronic structure of the system should be less sensitive to the specific doping site of Sr in LSMO.
Li1.4Al0.4Ti1.6(PO4)3 high lithium ion conducting solid electrolyte prepared by tape casting and modified with epoxy resin
Authors: Chen Qi  , Shang Xue-Fu  , Zhang Peng  , Xu Peng  , Wang Miao  , Nobuyuki Imanishi  ,   Department of Physics, Zhejiang University, Hangzhou 310027, China;,   Department of Physics, Jiangsu University, Zhenjiang 212013, China;,   Graduate School of Engineering, Mie University, Tsu 514-8507, Japan
Published: December 2020

The Li1.4Al0.4Ti1.6(PO4)3(LATP) nanocrystal powder is synthesized by citric acid assisted sol-gel method.The LATP powder is crystalized at 850℃ for 4 h,and the X-ray diffraction patterns show that the NASICON structure is obtained without any impurity phase.The LATP films are prepared by tape casting method through using as-synthesized LATP powder and subsequently recrystalized at various temperatures for 5 h.The impedance spectra of LATP film recrystalized at various temperatures indicate that the film sintered at 950℃ has the highest lithium ionic conductivity. Meanwhile,it is demonstrated that no impurity exists in LATP film recrystalizated at 950℃,and its lattice parameters are a=b=8.50236 Å and c=20.82379 Å.The high-purity LATP-epoxy films are prepared by modification with epoxy resin.The water permeation test proves that the LATP-epoxy film can prevent water from penetrating for 15 d,which indicates that epoxy resin fills the holes in LATP film.The fracture surface topography of LATP-epoxy film shows its dense structure with grain sizes from nano-scale to micro-scale.The energy dispersive X-ray spectrometer mapping of the fracture of LATP-epoxy film indicates that the carbon elements are uniformly distributed in grain boundary,which means that epoxy resin is soaked into LATP film.The relative density of 89.5% is obtained for LATP film,which is increased to 93.0% for LATP-epoxy (the nominal density is around 2.9624 g/cm3).The difference in relative density between LATP film and LATP-epoxy film indicates that the epoxy resin is immersed in LATP film already.The total,bulk,and grain boundary lithium ionic conductivities for the LATP film at 25℃ are 8.70×10-4 S·cm-1,2.63×10-3 S·cm-1 and 1.30×10-3 S·cm-1,respectively.The total,bulk,and grain boundary lithium ionic conductivities for the LATP-epoxy film at 25℃ are 3.35×10-4 S·cm-1,1.84×10-3 S·cm-1 and 4.09×10-4 S·cm-1,respectively.The decrease in the total conductivity of the LATP-epoxy film may be caused by the increase in its grain boundary resistance and its exposure to the atmosphere during modification with epoxy resin.The high lithium ionic conductivity for both LATP film and LATP-epoxy contributes to homogeneous mixture at sol-gel process and the decreasing of grain boundary impedance for this special structure.The activation energies for LATP film and LATP-epoxy film are 0.36 eV and 0.34 eV,respectively, based on Arrhenius equation.The water-impermeable high lithium ion conducting solid electrolyte of LATP modified with epoxy resin is likely to be used as protective film for lithium metal electrode of novel high energy density batteries.
First principle study of ternary combined-state and electronic structure in amorphous silica
Authors: Wan Ya-Zhou  , Gao Ming  , Li Yong  , Guo Hai-Bo  , Li Yong-Hua  , Xu Fei  , Ma Zhong-Quan  ,   SHU-SolarE R & D Lab, Department of Physics, College of Sciences, Shanghai University, Shanghai 200444, China;,   School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China;,   Instrumental Analysis and Research Center, Shanghai University, Shanghai 200444, China
Published: December 2020

In this paper, for the ITO-SiOx (In, Sn)/n-Si photovoltaic device, the molecular coacervate of In–O–Si bonding and two kinds of quantum states for indium-grafted in amorphous silicon oxide a-SiOx (In, Sn) layers are predicted by molecular dynamics simulation and density function theory calculation, respectively. The results show that the SiOx layers are the result of the inter-diffusion of the In, Sn, O, Si element. Moreover, In–O–Si and Sn–O–Si bonding hybird structures existing in the SiOx layers are found. From the result of formation energy calculations, we show that the formation energies of such an In–O–Si configuration are 5.38 eV for Si-rich condition and 4.27 eV for In-rich condition respectively, which are both lower than the energy (10 eV) provided in our experiment environment. It means that In–O–Si configuration is energetically favorable. By the energy band calculations, In and Sn doping induced gap states (Ev+4.60 eV for In, Ev+4.0 eV for Sn) within a-SiO2 band gap are found, which are different from the results of doping of B, Al, Ga or other group-Ⅲ and V elements. The most interesting phenomena are that there is either a transition level at Ev+0.3 eV for p-type conductive conversion or an extra level at Ev+4.60 eV induced by In doping within the dielectric amorphous oxide (a-SiOx) model. These gap states (GSⅡ and GSIS) could lower the tunneling barrier height and increase the probability of tunneling, facilitate the transport of photo-generated holes, strengthen the short circuit current, and/or create negatively charged defects to repel electrons, thereby suppressing carrier recombination at the p-type inversion layer and promoting the establishment of the effective built-in-potential, increasing the open-circuit voltage and fill factor. Therefore, the multi-functions such as good passivation, built-in field, inversion layer and carriers tunneling are integrated into the a-SiOx (In, Sn) materials, which may be a good candidate for the selective contact of silicon-based high efficient heterojunction solar cells in the future. This work can help us to promote the explanations of the electronic structure and hole tunneling transport in ITO-SiOx/n-Si photovoltaic device and predict that In–O–Si compound could be as an excellent passivation tunneling selective material.
Entropy forces of nanoparticles in self-propelled systems
Authors: Hua Yun-Feng  , Zhang Lin-Xi  ,   Department of Physics, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Entropy force is fairly ubiquitous in nature, but it is not practically beneficial for most cases, thus how to reduce the entropic force of the system is very important. In this paper, by employing the overdamped Langevin dynamics simulations, we explore the entropy force between two large nanoparticles (or two nanorods) immersed in a self-propelled system. Self-propelled particles can be regarded as active matter, and the active matter is an interesting subject which has been studied theoretically and experimentally over the past few years. A great many biological and physical systems can be referred to as active matter systems, including molecular motors, swimming bacteria, self-propelled colloids, motile cells, and macroscopic animals. Active matter obtains energy from an external system under non-equilibrium conditions, and active particles with suitably designed constructions are able to convert energy input into the desired control of function, which has wide potential applications in a diversity of fields, such as drug delivery in medicine. Self-propelled particles without angular velocity would gather around the nanoparticles (or nanorods) under the effect of entropy force, which can induce large entropy force between nanoparticles. The interaction force between two nanoparticles is large enough, owing to the asymmetry of the system, and entropy force also depends on the distance between two nanoparticles (or two nanorods). For the case of self-propelled particles with an angular velocity, the entropic effect is weak, and the larger the angular velocity, the weaker the entropic force is. Moreover, nanoparticles will no longer assemble together because of their weak entropic forces. Meanwhile, the entropy force between two nanorods can be tuned from a long repulsion into a long range attraction by changing the distance between two nanorods. The present investigation can help us understand the entropy forces in non-equilibrium systems.
Beam shearing characteristic analysis of interferometric hyperspectral imaging system
Authors: Li Jian-Xin  , Bai Cai-Xun  , Liu Qin  , Shen Yan  , Xu Wen-Hui  , Xu Yi-Xuan  ,   School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;,   MⅡT Key Laboratory of Advanced Solid Laser, Nanjing University of Science and Technology, Nanjing 210094, China}
Published: December 2020

A birefringent Fourier transform imaging spectrometer with a new lateral shearing interferometer is presented. The interferometer includes a Wollaston prism and a retroreflector. It splits an incident light beam into two shearing parallel parts to obtain interference fringe patterns of an imaging target, which is well established as an aid in reducing problems associated with optical alignment and manufacturing precision. The proposed method provides a direct technology for robust and inexpensive spectrometers to measure spectral signatures. Formulas for the optical path difference (OPD) produced by the proposed birefringent interferometer are derived by the ray-tracing method. Two experiments are carried out to demonstrate the accuracy of the formulas for OPD in the inner scanning mode and window scanning mode, respectively. A laser of wavelength 650 nm is used as a source of the experimental setup. The experimental estimations of the OPD and a reference OPD curve obtained with theoretical analysis are used for comparison. The match between the two curves is highly consistent, for the maximum deviation of the experimental OPD is less than /4. For the further verification of the imaging performance of the proposed method, another experiment is performed. A scene illuminated by an incandescent lamp is used as an imaging target. The temporal rotating of the retroreflector produces a series of time sequential interferograms, where the target is fixed and fringe patterns move. Performing nonuniform fast Fourier transform of the interferogram data produces a spectral data cube (i.e., the spectral images of the target).A series of recovered spectral images whose center wavelengths range from 450 to 650 nm is presented.In this paper, the principle of the instrument is described, and the OPD distribution formula is obtained and analyzed. The performance of the system is demonstrated through a numerical simulation and three experiments. This work will provide an important theoretical basis and the practical instruction for designing a new type of birefringent Fourier transform spectrometer based on Wollaston prism and its engineering applications.
Measurement of the fine structure of cesium Rydberg state
Authors: Pei Dong-Liang  , He Jun  , Wang Jie-Ying  , Wang Jia-Chao  , Wang Jun-Min  ,   Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China;,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Shanxi University, Taiyuan 030006, China;,   Collaborative Innovation Center of Extreme Optics, Taiyuan 030006, China}
Published: December 2020

The spectra of Rydberg atoms are of great significance for studying the energy levels of Rydberg atoms and the interaction between neutral atoms, especially, the high-precision spectra of Rydberg atoms can be used to measure the energy level shifts of Rydberg atoms resulting from the dipole-dipole interactions in room-temperature vapor cells. In this paper we report the preparation of cesium Rydberg states based on the cascaded two-photon excitation of 509 nm laser and 852 nm laser in opposite, and the measurements of the fine structure of cesium Rydberg states. In this experiment, the 509 nm laser is generated by the cavity-enhanced second-harmonic generation from 1018 nm laser with a periodically-poled KTP crystal and has a maximum power of about 1 W, and the 852 nm probe laser is provided by an external-cavity diode laser with a maximum output power of 5 mW and a typical linewidth of 1 MHz. By scanning the frequency of 509 nm coupling laser, it is presented that the Doppler-free spectra based on electromagnetically-induced transparency (EIT) of 509 nm coupling laser and 852 nm probe laser. The velocity-selective EIT spectra are used to study the spectral splitting of 6S1/26P3/257S(D) ladder-type system of cesium Rydberg atoms in a room-temperature vapor cell. The powers of 852 nm probe laser and 509 nm coupling laser are 0.3 upW and 200 mW, respectively. Their waist radii are both approximately 50 m. The intervals of hyperfine splitting of the intermediate state 6P3/2(F'=3, 4, 5) and fine splitting of 57D3/2 and 57D5/2 Rydberg states are measured by a frequency calibrating. Concretely, the velocity-selective spectrum with a radio frequency (RF) modulation of 30 MHz is used as a reference to calibrate the Rydberg fine-structure states in the hot vapor cell, where the RF frequency precision is smaller than a hertz on long time scales and the EIT linewidth is smaller than 13 MHz. The experimental value of the fine structure splitting of 57D3/2 and 57D5/2 Rydberg states is (354.72.5) MHz, that is in consistence with the value of 346.8 MHz calculated by Rydberg-Ritz equation and quantum defects of 57D3/2 and 57D5/2 Rydberg states. The experimental values of hyperfine splitting of intermediate state 6P3/2(F'=3, 4, 5) are also coincident with the theoretical calculated values. The dominant discrepancy existing between the experimental and calculated results may arise from the nonlinear correspondence of the PZT while the 509 nm wavelength cavity is scanned, and the measurement accuracy influenced by the spectral linewidth. The velocity-selective spectroscopy technique can also be used to measure the energy level shifts caused by the interactions of Rydberg atoms.