bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of symmetries of the substituted donor and acceptor on two-photon absorption cross sections of trans-stilbene derivatives
Authors: Su Yan  , Wang Chuan-Kui  , Wang Yan-Hua  , Tao Li-Min  ,   山东师范大学物理系,济南 250014
Published: December 2020

We have designed a series of trans-stilbene derivatives with different arrangement of the substituents and studied their one-photon and two-photon absorption properties by using the response theory methods at HF level. The calculations show that these molecules have strong two-photon absorption cross sections. In the visible light region, the maximum two-photon absorption cross section for molecules with asymmentric substitution of the donor and acceptor occurs in the first excited state, while for the symmetric substitution cases it occurs in the fourth excited state. The asymmetry-substituted molecules have a larger two-photon absorption cross section than the symmetry substituted molecules, indicating that the effect of the different kinds of substituents on the two-photon absorption of molecules is related to the property of theiry π-centers. The charge-transfer process for the charge-transfer states was visualized in order to understand their maximal two-photon absorption cross sections.
The second kind angular dispersion and the analysis of characteristics of diffraction grating
Authors: Bayanheshig  ,   中国科学院长春光学精密机械与物理研究所，长春 130033
Published: December 2020

The first and second kind formulas of angular dispersion, corresponding respectively to the polar angle and azimuthal angle of diffraction grating, are presented based on the generalized grating equation produced on the basis of vector diffraction theory under the condition of conical diffraction mounting; at the same time, by making theoretical and numerical analysis of the condition in which the second kind formula of angular dispersion changes evidently and the corresponding mathematical expression is obtained.
Quantum properties of light in the two-photon T-C model in Kerr medium
Authors: Fang Jia-Yuan  , Yan Xiao-Hong  , Zhou Ming  , Huang Chun-Jia  ,   (1)长沙理工大学物理与电子科学系,长沙 410077; (2)湘潭大学材料与光电物理学院,湘潭 411105; (3)湘潭大学材料与光电物理学院,湘潭 411105;长沙理工大学物理与电子科学系,长沙 410077
Published: December 2020

In this paper, the quantum properties of light in a system of two coupling atoms interacting with a single-model squeezed vacuum field at the two-photon transition in Kerr medium are studied by means of quantum theory.The influences of the Kerr medium and the dipole-dipole interaction between atoms are discussed. The results show that when the Kerr effect and the dipole-dipole interaction between atoms may be neglected, the fluctuation of U2 can be squeezed periodically. With increasing the Kerr effect and the dipole-dipole interaction between atoms, the squeezing effect of light gradually becomes weak and the squeezing time of light gradually decreases. The periodical collapse-revival phenomenon of the time evolution of the second-order coherence degree of the field appears, which is caused by the influence of the Kerr effect and the dipole-dipole interaction between atoms. No matter how large are the coupling constants, the photon bunching always appears.
The interactions between an atom and a field with a time-varying frequency
Authors: Xu Jing-Ping  , Yang Ya-Ping  ,   同济大学物理系，上海 200092
Published: December 2020

In this paper, the interactions between a two-level atom and a coherent field with a time-varying frequency have been studied. The two typical cases, in which the frequency of the field varies with time in the form of sine or impulse, have been considered. It is found that the collapse and revival phenomena of the atomic population inversion will disappear as the frequency changing with time in sine form; and the frequency varying in impulse form can lead to some new collapses and new revivals in the evolution of the atomic population inversion.
Optical properties of SrTiO3 and SrHfO3 by first principle calculations
Authors: Wang Yuan-Xu  , Wang Chun-Lei  , Zhong Wei-Lie  , Zhao Ming-Lei  , Li Ji-Chao  , Xue Xu-Yan  ,   山东大学物理与微电子学院，济南 250100
Published: December 2020

We have calculated the optical properties (the imaginary part of dielectric function ε2(ω), the optical absorption coefficient I(ω), the reflectivity R(ω) of SrTiO3 and SrHfO3 by the full potential linearized augmented plane wave (FLAPW)method. Through comparing their optical properties, we obtained the ifference between SrTiO3 and SrHfO3 and explained such a difference. Our calculated optical spectra have mainly four peaks around 4.4, 7.4, 8.3 and 23.6 eV, and the peak at about 4.4eV is sharp and high. Our calculated results are in good agreement with the experimental data.
Large optical cavity and small vertical divergence angle semiconductor lasers
Authors: Cui Bi-Feng  , Li Jian-Jun  , Zou De-Shu  , Lian Peng  , Han Jin-Ru  , Wang Dong-Feng  , Du Jin-Yu  , Liu Ying  , Zhao Hui-Min  , Shen Guang-Di  ,   北京工业大学北京市光电子技术实验室，北京 100022)
Published: December 2020

A novel coupled large optical cavity cascaded by tunnel-junction semiconductor lasers is put forward to resolve the major difficulties of ordinary laser diodes. In this structure several active regions are cascaded by tunnel junctions to couple a large optical cavity. This structure can solve the problem of catastrophic optical damage of facet and large vertical divergence caused by thin emitting area in ordinary laser diodes. The near-field facalur size reaches 1μm. Low-pressure metal-organic chemical vapor deposition is adopted to grow the novel semiconductor lasers. Slope efficiency as high as 0.80W/A per facet and vertical divergence angle of 20°and threshold current density of 277 A/cm2 are achieved from an uncoated novel laser device.
Edge-pumped composite thin-disc Yb:YAG/YAG laser: design and power scaling
Authors: Liu Qiang  , Gong Ma-Li  , Pan Yuan-Yuan  , Li Chen  ,   清华大学精密仪器与机械学系，北京 100084
Published: December 2020

The design uses a composite Yb:YAG/YAG disc laser configuration with the pump light incident from the disc edge. The crucial advantages of the thin-disc design is that the thermal gradients are aligned with the beam propagation direction, the transverse temperature gradients are reduced, previous difficulties with high average power pumping/cooling and the rejection of amplified spontaneous emission are resolved. In contrast to high power rods or slabs, the one-dimensional nature of the cooling geometry and the edge-pump geometry scale gracefully to very high average power. Two point designs illustrating power scaling are also given as examples.
Theoretical and experimental investigations on a novel tunable all-optical wavelength converter
Authors: Xu Fan  , Zhang Xin-Liang  , Huang De-Xiu  ,   华中科技大学光电子工程系，武汉 430074
Published: December 2020

Tunable wavelength converters are key components in intelligent all-optical network. In this paper, a novel scheme for tunable wavelength conversion based on semiconductor-fiber ring laser is proposed. Probe laser in the conventional scheme could be left out and self-started tunable wavelength conversion could be achieved. Theoretical model for this novel scheme is also established and the output characteristics are calculated. Experimental results show good agreement with theoretical results. In experimental study, 2.5Gb/s tunable XGM wavelengthconversion with 40nm tuning range was demonstrated. Experimental and theoretical studies show that this novel scheme is worthy of further investigation.
Nonlinear propagation and power limiting of nanosecond laser pulse by stimulated Brillouin scattering in CCl4
Authors: Lü Yue-Lan  , Lü Zhi-Wei  , Dong Yong-Kang  ,   哈尔滨工业大学光电子技术研究所,哈尔滨 150001
Published: December 2020

Based on the quasi-steady stimulated Brillouin scattering theory, the nonlinear propagation of 1.064μm, YAG nanosecond pulsed light was analyzed numerically and treated with a theoretical model that includes the spontaneous nature of the initiation of stimulated Brillouin scattering(SBS). Then the pulse propagation and power limiting effects (including both power limiting and energy limiting) were obtained in the SBS process. The temporal pulse reshaping and power limiting have been given graphically on SBS mechanism with a nonlinear medium CCl4 for various pump energies and pulse-width (10ns). The power transmission properties and delay time of the power limiting effect depending on pump energy were given theoretically. And the influence of pump energy on the transmitted pulse profiles and delay time were investigated experimentally. The numerical simulations of transmitted pulse characteristics were in good agreement with the experimental results.
Theoretical analysis of hot image effect from phase scatterer
Authors: Xie Liang-Ping  , Zhao Jian-Lin  , Su Jing-Qin  , Jing Feng  , Wang Wen-Yi  , Peng Han-Sheng  ,   (1)西北工业大学应用物理系,西安 710072; (2)西北工业大学应用物理系,西安 710072;中国工程物理研究院激光聚变研究中心,绵阳 621900; (3)中国工程物理研究院激光聚变研究中心,绵阳 621900
Published: December 2020

The nonlinear hot image effect from phase scatterer in a high-power laser system has been investigated theoretically and numerically. According to the Fresnel-Kirchhoff diffraction integral and nonlinear paraxial wave equation, we derive the functional relationship of the intensity of hot image and its location. It is shown that the image intensity is likely several times larger than that from amplitude scatterer, and the location is situated in the equidistant downstream plane of the scatterer in an optical component located upstream from a nonlinear element. Good agreements are shown between the theoretical prediction and the computer codes developed for ns-pulse propagation simulations. The results indicate that the formation of hot image is akin to the real-time, in-line and volume-phase holographic imaging.
Optimal design of the active regions for InGaAsSb/AlGaAsSblong wavelength multi quantum well lasers
Authors: Xu Gang-Yi  , Li Ai-Zhen  ,   中国科学院上海微系统与信息技术研究所，信息功能材料国家重点实验室，上海 200050
Published: December 2020

We present a theoretical study of the optical gain of InGaAsSb/AlGaAsSb type-I quantum well lasers, whose lasing wavelength is designed to be 2.7μm. A self-consistent solution, which solves the Schrdinger equations and Poisson equation simultaneously, is used to calculate the band structure and gain spectra of the quantum wells. By studying the influence of strain and width of the well material, we find that the main factor limiting the optical gain is not the optical matrix element, but the population inversion, especially the probability to find a hole in the first valence subband. Increasing the compressive strain or (and) decreasing the well width will enlarge the optical gain. The former lowers the in-plane effective mass of the hole. Although the latter slightly increases the in-plane effective mass of holes, it does enlarge the energy separation of the valence subbands. Both effects lower the total state density near the valence edge, and finally enlarge the optical gain. Our theoretical results can explain qualitatively the reported experimental results, and are useful for the design of InGaAsSb/AlGaAsSb long wavelength quantum well lasers.
Redshift of harmonics by laser interaction with solid target
Authors: Zhang Qiu-Ju  , Sheng Zheng-Ming  , Zhang Jie  ,   中国科学院物理研究所光物理开放实验室，北京 100080
Published: December 2020

Using the one dimensional particle in cell simulation code, we have studied the generation and redshift of harmonics from overcritical plasma layer irradiated by ultrashort intense laser pulses. Except for the strong oscillations of target surface driven by the laser field, the light pressure of the intense laser can ablate and push the target suface, which is the reason for the redshift of harmonics.
Dynamics of nonphase-locking Lorenz-Haken equation
Authors: Ju Rui  , Zhang Ya-Jun  , Huang Hong-Bin  , Zhao Huan  ,   东南大学物理系，南京 210096
Published: December 2020

Considering the atomic coherences and injected classical field, we derived the n-Onphase-locking Lorenz-Haken equation by using the technique of stochastic differential equations. The effects of detuning, injected field and the atomic coherence on the dynamical characteristics of this equation is then numerically studied. The results show that in laser working situations, the detuning can result in chaotic behaviors of the light phase. Under different conditions, the system can generate four attractors, double attractors and single attractor, and the fractal dimension of the system is larger than that of the locking-phase system. The optical detuning, injected field and atomic coherence can inhibit the chaos of the cavity field. In the optical bistability regions, we obtain symmetric bistability pair, but never find the chaotic attractors.
Theoretical study of the tunable optical filter properties based on photonic crystals
Authors: Mao Hui-Bing  , Yang Chang-Li  , Lai Zong-Sheng  ,   华东师范大学信息科学技术学院，上海 200062
Published: December 2020

The transmission properties of the one-dimensional photonic crystals with defects were studied using the eigen matrix method, and a new kind of tunable optical filter is proposed in this paper. When the one-dimensional photonic crystals (L1H1)m have defects such as LcH2(L2H2)n, there will be a narrow transmission band in the gap of the photonic crystals, meanwhile the other transmission peak will weaken and disappear with the increase of the periodic number of the cover layer. When the thickness of the couple layer changes, there will be two regions with high transmittivity besides the edges of the photonic crystals gap. The properties of the high transmission band depend on the photonic crystals and the cover layers. When the photonic crystals gap is narrowed, the two regions will come near, which results in a wide transmission region about 150 nm. A new kind of tunable optical filter thus can be fabricated based on this phenomenon by the surface micro-mechanical technology.
The defect effect in the one-dimensional negative permeability material
Authors: Zhao Qian  , Zhao Xiao-Peng  , Kang Lei  , Zhang Fu-Li  , Liu Ya-Hong  , Luo Chun-Rong  ,   西北工业大学电流变技术研究所,西安 710072
Published: December 2020

It was shown theoretically and experimentally that a metamaterial composed of periodically positioned split ring resonators (SRR) can lead to a negative effective permeability μeff close to its resonance frequency. In this paper, the nearest neighbor interactions between hexagon SRR were investigated in experiment. The experimental results show that there is only one resonance frequency for a one-dimensional negative permeability μeff material. The main and defect resonance frequencies have a shift when the defect SRR is introduced into the materials, and the shifts of which increase with the resonance frequency difference between defect and based SRR. It is thought that the interaction between SRR becomes stronger when the resonance frequency of the defect SRR is close to that of the based SRR.
Chirped pulse cross-correlation for THz wave measurement
Authors: Shen Jing-Ling  , Zhang Cun-Lin  , Hu Ying  , S. P. Jamison  ,   (1)Department of Physics,University of Strathclyde,Glasgow G4 0NG,United Kingdom; (2)首都师范大学物理系,北京 100037
Published: December 2020

We introduce a technique, chirped pulse cross-correlation, for single shot THz detection. The time-resolution limitation of previously demonstrated single-shot amplitude modulation spectral encoding is analyzed. The new technique is free from the limitation.
Experimental and theoretical study on the ablation of fused silica by femtosecond lasers
Authors: Deng Yun-Pei  , Jia Tian-Qing  , Leng Yu-Xin  , Lu Hai-He  , Li Ru-Xin  , Xu Zhi-Zhan  ,   中国科学院上海光学精密机械研究所，上海 201800
Published: December 2020

In this paper we report the measurements of the damage threshold and ablation depth for fused silica by laser pulses at the wavelength of 800 nm, with the pulse duration ranging from 45 to 800fs. These results can be well understood by using an improved avalanche model. The model includes the production of conduction band electrons(CBE), laser energy deposition, and CBE diffusion. The evolution of micro-explosion is investigated based on this model.
The sweep down flow and “contra-hairpin vortex” in a turbulent boundary layer
Authors: Lian Qi-Xiang  , Guo Hui  ,   北京航空航天大学流体力学研究所，北京 100083
Published: December 2020

The sweep down flow and related flow structures in a turbulent boundary layer were visualized with hydrogen bubble method. The streamwise and transverse vortices induced by sweep down flow near the wall of a vessel were observed. A new kind of vortical structure, whose features are contrary to those of the hairpin vortex, was observed in the present experiments. It is termed “contrahairpin vortex” here. Its head points upstream, while the head of a hairpin vortex points downstream; lift-up flow is induced between the legs of a hairpin vortex, while between the legs of this new vortical structure, sweep down flow is induced.
An auxiliary differential equation FDTD method for anisotropic magnetized plasmas
Authors: Liu Shao-Bin  , Mo Jin-Jun  , Yuan Nai-Chang  ,   (1)国防科学技术大学电子科学与工程学院，长沙 410073; (2)国防科学技术大学电子科学与工程学院，长沙 410073;南昌大学数理学院，南昌 330029
Published: December 2020

An auxiliary differential equation finite-difference time-domain (ADE-FDTD) methodology for anisotropic magnetized plasmas is derived. The method is based on a difference approximation of the auxiliary differential equation. A comparison with the JEC method is included. The CPU time saving by several times and accuracy of the method are confirmed by computing the reflection and transmission through a magnetized plasma layer, with the direction of propagation parallel to the direction of the biasing field.
Target ablation characteristics during pulsed laser deposition of thin films
Authors: Zhang Duan-Ming  , Hou Si-Pu  , Guan Li  , Zhong Zhi-Cheng  , Li Zhi-Hua  , Yang Feng-Xia  , Zheng Ke-Yu  ,   (1)湖北襄樊学院物理系,襄樊 441053; (2)华中科技大学物理系,武汉 430074;华中科技大学激光技术国家重点实验室,武汉 430074
Published: December 2020

The whole ablation process of target heated by pulsed lasers is studied in this paper. Under the appropriate dynamic boundary conditions, have been investigated in detail the heat flow equation with heat generation term, and the temperature distribution of target before and after the melting. In particular, after target melting, the temperature distribution and the interface position between the solid and liquid phases as functions of time are presented in the solution of analytical expressions. Additionally, under the energy balance conditions, the dependence of the ablating surface position on the time is investigated. Consequently, the ablation of target Si has been calculated. This research shows a positive result compared with the relevant experiments.
Experimental studies of Z-pinches of mixed wire array with aluminum and tungsten
Authors: Ning Cheng  , Li Zheng-Hong  , Hua Xin-Sheng  , Xu Rong-Kun  , Peng Xian-Jue  , Xu Ze-Ping  , Yang Jian-Lun  , Guo Cun  , Jiang Shi-Lun  , Feng Shu-Ping  , Yang Li-Bing  , Yan Cheng-Li  , Song Feng-Jun  , V. P. Smirnov  , Yu. G. Kalinin  , A. S. Kingsep  , A. S. Chernenko  , E. V. Grabovsky  ,   (1)Russia Research Center “Kurchatov Institute ",Moscow,Russia; (2)Troitsk Institute for Innovation and Fusion Research,Troitsk,Russia; (3)中国工程物理研究院，绵阳 621900
Published: December 2020

In the form of joint experiment between China and Russia, the experimental studies of Zpinches of mixed wire array of aluminum (A1) and tungsten (W) were carried out on S-300 generator,which was located on Kurchatov Institute of Russia. The experimental results were compared with those of single A1 array and single W array, respectively. There are obvious difference between mixed one and single one in their photon spectral distributions. The intensity of K-series emission lines from the mixed wire array Z-pinch is lower than that from single A1 array. The radiated lines with wavelengths less than 1.6nm were not found in single W array Z-pinches. In the Z-pinch processes, the area radiating x-arys in mixed wire array is smaller than that of single A1 array, but is larger than that of single W array. The radiated energy from mixed wire array Z-pinch is higher than that from single A1 array, but is slightly lower than that from single W array. The FWHM of x-ray pulse with a maximal power 0.3—0.5TW and total energy 10—20kJ is about 25ns, which radiated from Z-pinches with a radial convergence of 4—5 on S-300 generator. The shadow photograph of the mixed wire-array Z-pinch plasma by laser probe shows that the core-corona configuration was formed and the corona was moving toward the center axis during the wire-array plasma formation, that the interface of the plasma is not clear, and that therer are a number of structures inside. They also suggests that there was an obvious development of Magneto Rayleigh-Taylor instability in the Z-pinch process as well.
The study on the efficient method for producing large amount of single-walled carbon nanotubes with recirculated arc discharge
Authors: Wang Xin-Qing  , Wang Miao  , Li Zhen-Hua  , Liu Zi-Yang  ,   (1)浙江大学化学系,杭州 310027; (2)浙江大学力学系,杭州 310027; (3)浙江大学物理系,杭州 310027;浙江大学微系统研究与开发中心,杭州 310027
Published: December 2020

By using Y-Ni-C composite rod as cathode, large amount of single-walled carbon nanotubes was produced by an improved arc discharge method, in which a tungsten rod was used as an electrode and the electrodes were exchanged after each discharge. The raw soot was characterized by high resdution electron microscope and Raman spectrum, and the results show that this is an efficient way to produce large amount of single-walled carbon nanotubes.
Field emission from individual vertically carbon nanofibers
Authors: Li Hai-Jun  , Gu Chang-Zhi  , Dou Yan  , Li Jun-Jie  ,   (1)中国科学院物理研究所表面物理国家重点实验室,北京 100080; (2)中国科学院物理研究所表面物理国家重点实验室,北京 100080;北京工业大学材料科学与工程学院,北京 100022
Published: December 2020

Individual high-aspectratio carbon nanofibers(CNFs) were grown on W wire by plasma-enhanced hot filament chemical vapor deposition method, using a gas mixture of methane and hydrogen. The average diameter and length of carbon nanofibers are 60—100 nm and 6—30 μm, respectively, and the density of carbon nanofibers is less than 10.6cm-2. The field emission properties from individual carbon nanofibers have been measured using a movable W probe with a low-curvature radius. The results indicated that the CNFs showed a turn on field of about 5 V/μm and the field-emission current density of 20μA/cm2 at 5 V/μm.The experimental data also indicated that the length of CNFs and the position of a CNF are responsible for the properties of field emission related to the parameters such as the work function of materials, applied field and the field amplification factor. Furthermore, the electron scattering induced by defects in CNFs is also a key factor on the field-emission current.
Extraordinary Hall effect in FexSn100-x granular alloy films
Authors: Gao Jun  , Jiang Xiao-Long  , Ren Shang-Kun  , Ni Gang  , Zhang Feng-Ming  , Du You-Wei  ,   南京大学固体微结构物理国家重点实验室 南京 210093
Published: December 2020

A series of FexSn100-x granular alloy films with different atomic fractions were fabricated by ion beam sputtering. The highest value ever observed for ferromagnetic metal/non-magnetic metal systems has been obtained. The extraordinary Hall effect was studied systemically by varying the atomic fractions and the thickness of the samples. With the power law between the saturated Hall resistivity and the resistivity the mechanism of the extraordinary Hall effect was also discussed.
Investigation of a-Si:H film characteristics influenced by magnetic field gradient in MWECR CVD plasma system
Authors: Hu Yue-Hui  , Yin Sheng-Yi  , Chen Guang-Hua  , Wu Yue-Ying  , Zhou Xiao-Ming  , Zhou Jian-Er  , Wang Qing  , Zhang Wen-Li  ,   (1)北京工业大学材料科学与工程学院,北京 100022; (2)景德镇陶瓷学院,景德镇 333001
Published: December 2020

In this paper the magnetic field profiles produced by coil currents of I=115.2A，I=137.7A and I=137.7A with a SmCo permanent magnet under the substrate holder in the deposition chamber and plasma chamber in the single-coil divergent field MWECR(micro-wave electron cyclotron resonance) CVD system was investigated. Then the magnetic field gradient of these magnetic field profiles was obtained quantitatively using Lorentz fit. The results indicated that the gradient value nearby the substrate, which was produced under the condition that the magnetic field profiles are produced by the coil current 137.7A with a SmCo permanent magnet under the substrate holder, is the largest, the larger one being produced by the coil current of 137.7A without the permanent magnet and the smallest one being produced by coil current of 115.2A. The effect of magnetic field gradient on characteristics of a-Si:H film has been also analyzed. It was found that high deposition rate was observed nearby the substrate with a high magnetic field gradient and that the better photosensitivity of a-Si:H film could be obtained at the lower substrate temperature when magnetic field gradient is high.
Morphological characterization and nanoindentation hardness scatter evaluation for Cu-W thin films based on wavelet transform
Authors: Wang Yuan  , Bai Xuan-Yu  , Xu Ke-Wei  ,   (1)西安交通大学金属材料强度国家重点实验室,西安 710049; (2)西安交通大学金属材料强度国家重点实验室,西安 710049;兰州铁道学院机械与动力学院,兰州 730070
Published: December 2020

A strategy based on wavelet transform to describe surface morphology of thin films is presented in this paper.The evolution of surface morphology of Cu-W thin films with deposition time on silicon wafers was investigated by discrete wavelet transform (DWT) method. The results show that the surface morphology of the thin films is unstable until the sputtering time exceeds 10 min. The surface morphology variation of different thin films can be distinguished primarily by high frequency signals.A scattering of the nanoindentation hardness values, which results from the roughness of the thin films surface, can be characterized by the roughness defined by the surface texture based on wavelet transform.
The phonon and energy splitting in the D3d minima for the T1u×hg Jahn-Teller system
Authors: Qiu Qing-Chun  ,   汕头大学医学院物理与信息学系,汕头 515031
Published: December 2020

In C60 molecules, the lowest unoccupied molecular orbital has T1u symmetry. The orbital is easily occupied by an electron through molecular inner excitation or doping and becomes an active Jahn-Teller (JT) electronic state. The T1u-hg- JT system is formed by the coupling of such an electronic state to a five-fold degenerate hg mode. The linear vibronic coupling in the system forms a trough on the adiabatic potential surface of the system, but D5d and D3d minima will be warped while considering the quadratic vibronic coupling. Phonon states in minima will have anisotropic effects and the vibrational frequencies should be different in different directions. This phenomenon will further affect the energy distribution, phonon overlap and tunneling effect in the system. The anisotropic effect is carefully studied in detail for D3d-minima. The energies and vibrational frequencies are calculated using unitary shift transformation, pick-Pryce method, scale transformation and energy minimization procedure. The energy gap and the variation of perturbation energy in minima are obtained in this paper and the same physical quantities in trough are derived through changing the values of the quadratic coupling constants.
Studies on the structure and transport properties for Y-doped La2/3Ca1/3MnO3 perovsksite manganate
Authors: Zhang Yu-Feng  , Zhang Jin-Cang  , Wang Xin-Yan  , K. Tubata  , Liu Yong-Sheng  , Shu Yang  , Jing Chao  , N. Nishimura  , K. Mori  , Cao Shi-Xun
Published: December 2020

The structure and transport properties of perovskite (La1-xYx)2/3Ca1/3 MnO3 (0≤x≤0.3) systems are systematically investigated. It is found that all the compounds show a single phase structure. With the increase of Y3+ doping content the metalinsulator transition temperature TMI(M—I) shifts to lower temperatures. While the relevant resistance peak ρp is sharply increased, for the sample of x=0.3, it has been enhanced by eight orders of magnitude larger than the non-doped sample(x=0.0). In these materials a large magnetoresistance effect has been observed under an external magnetic field. At the same time, it is also directly shown that the correlation between the transport properties and the variation of crystal structure from the experiment result. Based on the double exchange model and the variable-range-hopping(VRH) theory, the mechanism of the influence of Y doping for La in La2/3Ca1/3MnO3 systems is also discussed.
Study on the high-resolution thermoelectric power of metallic state quasi-one-dimensional organic superconductor of (TMTSF)2ClO4 salt
Authors: Chai Yi-Sheng  , Yang Hong-Shun  , Liu Jian  , Ji Ming  , Bai Yan-Bo  , Cao Lie-Zhao  , J. C.Lasjaunias  ,   (1)Centre de Recherches sur les Tres Basses Temperatures,Laboratoire associe a l'Universite Joseph Fourier,CNRS,BP 166 38042,Grenoble Cedex 9,France; (2)中国科学技术大学结构分析开放实验室，物理系,合肥 230026
Published: December 2020

We investigate the high-resolution thermoelectric power of Bechgaard salt (TMTSF)2ClO4 in temperatures between 6 and 280K for metallic state with different cooling rates through the anion-ordering transition Ta=24K. There is a linear temperature-dependent thermoelectric power at high temperatures, which cannot be explained by conventional one-dimensional(1D) electron band theory. A sudden change of the slope at about 240K is observed for the first time. Below 140K, the curve deviates from linear behavior and goes down all the way through, which is attributed to a 1D—2D crossover. Comparing with the results of specific heat and resistivity with different cooling rates through the anion-ordering transition at 24K, no clear trace of anion-ordering transition can be spotted in thermoelectric power by the slowest cooling process unless we take differentiation of the data and we found a gradual rise in thermoelectric power with increasing cooling rate through the Ta for the first time. The influence of anion-ordering transition is discussed.
High-order harmonic attosecond pulses driven by a two-pulse laser
Authors: Zeng Zhi-Nan  , Li Ru-Xin  , Xie Xin-Hua  , Xu Zhi-Zhan  ,   中国科学院上海光学精密机械研究所,上海 201800
Published: December 2020

The scheme of attosecond high-order harmonic generation driven by a two-pulse laser field is proposed. Calculated results show that, not only a single attosecond x-ray pulse can be produced with two pulses, which may break the energy limitation of the few-cycle pulse, but also the intensity is even higher than that generated by a single laser pulse with the same intensity.
Influence of polarizations and doping in AlGaN barrier on the two-dimensional electron-gas in AlGaN/GaN heterostruture
Authors: Kong Yue-Chan  , Zheng You-Dou  , Zhou Chun-Hong  , Deng Yong-Zhen  , Gu Shu-Lin  , Shen Bo  , Zhang Rong  , Han Ping  , Jiang Ruo-Lian  , Shi Yi  ,   南京大学物理系,南京 210093
Published: December 2020

The two-dimensional electron-gas (2DEG) distribution, sheet density and subband occupations in AlxGa1-xN/GaN heterostructure are calculated by solving the coupled Schrdinger and Poisson equations selfconsistently. By involving degree of relaxation to distinguish the spontaneous and piezoelectric polarizations, the influence of the polarizations and the doping in the AlGaN barrier on the 2DEG properties are investigated separately. It is found that the 2DEG properties depend much stronger on the polarizations than on the doping, and that the contribution of the spontaneous polarization is dominant. The 2DEG sheet density is calculated to be 1.6×10-13cm-2 with an Al-content of x=0.3 in the strained AlGaN barrier, the contributions of spontaneous and piezoelectric polarizations are 0.9×10-13 and 0.7×10-13cm-2 respectively. When the doping of the AlGaN barrier is increased from 1×10-17 to 1×10-18cm-3, the 2DEG sheet density is increased by 0.2×10-13cm-2
Multicomponent excited-state emissions in a bilayer organic electroluminescent device
Authors: Zhu Wen-Qing  , Wu You-Zhi  , Zheng Xin-You  , Jiang Xue-Yin  , Zhang Zhi-Lin  , Sun Run-Guang  , Xu Shao-Hong  ,   上海大学材料科学系,上海 201800
Published: December 2020

Multicomponent excited-state emissions from monomer, exciplex and electroplex were observed in a bilayer organic electroluminescent device with a structure of ITO/TPD(60nm)/PBD(60nm)/Al(where TPD and PBD stand for N,N′diphenylN,N′bis(3-methylphenyl)1,1′biphenyl4,4′diamine) and (2(4′biphenyl)5(4″tertbutylphenyl)1,3,4oxadiazole, respectively). The difference between the photoluminescence of this device and the TPD∶PBD equimolar evaporated films suggests that the exciplex takes place only at the interface of TPD/PBD. The Variation of electroluminescence spectra with bias indicates the different formation mechanisms and the different population of each excited state component, as well as the different dynamic recombination process of carriers in this device.
Magneto-coupling effect on surface electron states in a semi-infinite superlattice
Authors: Huang Wei-Qing  , Chen Ke-Qiu  , Shuai Zhi-Gang  , Wang Ling-Ling  , Hu Wang-Yu  ,   (1)湖南大学应用物理系，长沙 410082; (2)湖南大学应用物理系，长沙 410082;中国科学院化学研究所有机固体重点实验室，北京 10008; (3)中国科学院化学研究所有机固体重点实验室，北京 10008
Published: December 2020

A theoretical study, within the effective-mass approximation, on the coupling effects of applied magnetic fields along the growth direction of the superlattice on the surface electron states in a semi-infinite semiconductor superlattice is presented by using an effective-barrier height method. The coupling effect is necessarily considered when the difference of the electron effective masses between different materials cannot be neglected. Our numerical results show that the magneto-coupling effect brings about not only the splitting of the surface electron levels but also the definite dependence of the surface levels and its localization degree on magnetic fields and Landau indices. Our results also indicate that the imaginary component of Bloch wave number can serve as a measure of the localization degree of the surface electron states.
The persistent current in a mesoscopic Aharonov-Bohm ring with a series-coupled double quantum dot
Authors: Wu Shao-Quan  , Chen Xiong-Wen  , Sun Wei-Li  , Wang Shun-Jin  ,   (1)四川师范大学物理系，成都 610068; (2)西南交通大学现代物理研究所，成都 610031
Published: December 2020

We study theoretically the properties of the ground state of a mescopic ring with a seriescoupled double quantum dot in the Kondo regime by means of the two-inpurity Anderson Hamiltonian. The Hamiltonian is solved by means of the slave-boson mean-field theory. It is shown that two dots can be coupled coherently, which is reflected in the appearance of parity effects and the complex current-phase relation in this system. This system might be a possile candidate for future device applications.
Magnetic properties and colossal magnetoresistance effect in perovskite-type manganite Ca(Mn2Cu1)Mn4O12
Authors: Xia Hong-Xu  , Yan Jun  , Yu Jiang-Ying  , Zhang Shi-Yuan  ,   南京大学物理系，固体微结构物理国家重点实验室，南京 210093
Published: December 2020

The perovskitetype manganites Ca(Mn2Cu1)Mn4O12 were prepared using the conventional solid state reaction method. X-ray diffraction patterns show that the annealing in air at 1073 K after the first sintering at higher temperatures can reduce the volumetric percentage of impurity phases in samples. Magnetic measurements indicate that the samples exhibit ferromagnetic antiferromagnetic transitions at low temperatures. Magnetization of the samples at 4.5 K is greatly decreased due to the existence of the antiferromagnetic phase, and shows no sign of saturation at 4.5 K and a magnetic field up to 8 T. The samples show semiconducting behavior. Their MR ratio reaches -35%—-46% at the temperature of 85 K and the magnetic field of 6 T.
Determination of bandgap in SiGe strained layers using a pn heterojunction C-V
Authors: Shu Bin  , Dai Xian-Ying  , Zhang He-Ming  ,   西安电子科技大学微电子研究所，西安 710071
Published: December 2020

A pn heterojunction C-V technique used to determine the bandgap of SiGe strained layers is presented in this paper. The SiGe bandgap is analyzed and calculated by acguiring the built-in potential and discontinuities of valence and conduction bands, according to the C-V profile of the stained SiGe/Si pn heterojunction. This technique is much more convenient and the experimental results agree very well with the theoretical and published calculations, indicating that the method is correct. This method is suitable for not only the bandgap of the single SiGe/Si pn heterojunctions, but also that of the SiGe/Si devices with SiGe/Si pn heterojunctions.
In-plane ferromagnetic resonance in nano-composite Fe-R-O（R=Hf Nd Dy）films
Authors: Du Jun  , Sun Liang  , Sheng Wen-Ting  , You Biao  , Lu Mu  , Hu An  , M. M. Corte-Real  , J. Q. Xiao  ,   (1)Department of Physics and Astronomy,University of Delaware,Newark,DE 19716,USA; (2)南京大学物理系，固体微结构物理国家重点实验室，南京 210093
Published: December 2020

Fe-R-O (R=Hf, Nd and Dy) films were made by reactive sputtering technique and annealed at 400℃. X-ray diffraction and electron diffraction show that nanometer scale Fe grains are embedded in amorphous Roxide matrix. Inplaneferromagnetic resonance was systematically carried out to measure the inplaneresonance absorption spectra and utilized to analyze the relationship between the local magnetization and grain size. The asdeposited samples show obvious uniaxial anisotropy, while annealed samples display weak magnetic crystalline anisotropy at the expense of weakening the uni-axial anisotropy. The local magnetization was calculated based on the formula. (ω/γ)2=(Hres+HK)(Hres+HK+4πMs).It decreases with decreasing grain size, being as only about 30% of the saturation magnetization of bulk Fe. It is also smaller than the bulk magnetization calculated according to the volume ratio of Fe. The linear dependence on the inverse of the grain size indicates a strong surface moment pinning effect.
Enhanced piezoelectric properties of (Bi0.5Na0.5)1－xBax TiO3 lead-free ceramics by sol-gel method
Authors: Zhao Ming-Lei  , Wang Chun-Lei  , Wang Jin-Feng  , Chen Hong-Cun  , Zhong Wei-Lie  ,   山东大学物理与微电子学院，晶体材料国家重点实验室，济南 250100
Published: December 2020

The dielectric, piezoelectric, ferroelectric and pyroelectric properties of (Bi0.5Na0.5)1-xBaxTiO3 (x=0.00，0.04，0.06，0.08, 0.12) ceramics prepared by sol-gel method were investigated. It was found that all the samples in this experiment show improved piezoelectric properties,obtained by using this chemical method. For(Bi0.5Na0.5)0.94Ba0.06TiO3 ceramic, as its composition is near the morphotropic phase boundary (MPB), it shows the largest piezoelectric constant, d33=173×10-12C/N, which is about 40% improvement compared to the conventional processed ceramics in this system. In addition, from the ferroelectric and pyroelectric measurements, the remanent polarization Pr, coercive field Ec and depolarization temperature Td of the (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramic were found to be 25μC/cm2, 28kV/cm, and 80℃, respectively.
Analysis of the reflective performance of EUV multilayer under the influence of capping layer
Authors: Wang Hong-Chang  , Wang Zhan-Shan  , Li Fo-Sheng  , Qin Shu-Ji  , Du Yun  , Wang Li  , Zhang Zhong  , Chen Ling-Yan  ,   同济大学精密光学工程技术研究所，物理系，上海 200092
Published: December 2020

In this paper we present a solution that addresses the reflectance loss due to oxidation. The solution is a capping layer (CL) that acts as an effective oxidation barrier when the multilayer (ML) is exposed to the extreme ultraviolet (EUV) light in the presence of water vapor, so that the optical element of multilayer can be used as long as possible. The theoretical reflectivity of ML Mo/Si EUV mirrors is calculated at 13.9nm under the different CL materials. The thicknesses of the CL and standard ML are optimized by the simplex method, meanwhile the reflectivity of ML can be further enhanced when the layer by layer theory is used. Finally the electric-field intensity distribution in the top layers of the ML is analyzed when the CL is added.
The effect of baking temperature on the crystal structure and ferroelectric properties of Bi3.25La0.75Ti3O12 thin films prepared by sol-gel processing
Authors: Wang Qiang  , Shen Ming-Rong  , Hou Fang  , Gan Zhao-Qiang  ,   苏州大学物理系，苏州 215006
Published: December 2020

The crystal structures, surface morphology and ferroelectric properties of Bi3.25La0.75Ti3O12 (BLT) thin films were found to be greatly affected by the baking temperature during sol-gel processing. At lower baking temperatures, the (117) orientation in the BLT thin film was preferred. However, with the increase of baking temperature, the (117) diffraction peak became weaker. In addition, the surface morphology of the films changed from rodlike to platelike. The ferroelectric properties were measured and it was found that the BLT thin film has the largest remnant polarization (2Pr) 284μC/cm2 prepared at a baking temperature of 250℃.
Solidification of FeSi2 alloy under high pressure
Authors: Wang Hai-Yan  , Liu Ri-Ping  , Ma Ming-Zhen  , Gao Ming  , Yao Yu-Shu  , Wang Wen-Kui  ,   (1)燕山大学亚稳材料制备技术与科学重点实验室，秦皇岛 066004; (2)燕山大学亚稳材料制备技术与科学重点实验室，秦皇岛 066004;中国科学院物理研究所，北京 100080
Published: December 2020

Influence of pressure on solidification microstructure of FeSi2 alloy is investigated. Different from the eutectic structure of the sample solidified at normal pressure, the microstructure of the sample solidified at high pressure is composed of dendritic primary phase and anomalous eutectic. The significant change in microstructure results from the change of phase diagram and solute atom diffusion induced by high pressure. By introducing the pressure parameter, the constitution undercooling criterion is attained. Formation mechanism of dendritic primary phase under high pressure is analysed according to the constitution criterion.
Experimental study on the hydrogen storage and release in nano-graphite synthesized by explosive detonation
Authors: Wen Chao  , Jin Zhi-Hao  , Li Xun  , Sun De-Yu  , Guan Jin-Qing  , Liu Xiao-Xin  , Lin Ying-Rui  , Tang Shi-Ying  , Zhou Gang  , Lin Jun-De  ,   (1)西安交通大学金属材料强度国家重点实验室，西安 710049; (2)西安交通大学金属材料强度国家重点实验室，西安 710049;西北核技术研究所，西安 710024; (3)西北核技术研究所，西安 710024
Published: December 2020

In this article, synthesis of nanographite powders using pure TNT ( trinitrotoluene )explosives is reported. X-ray Diffraction (XRD) results indicated that the detonation product has a hexagonal-graphite structure and the average size of the particles of graphite is 1.86—2.61nm. Specific surface area of nano-graphite is about 500—650m2/g measured by BET gas sorption instrument.Crystal grain size of the nano-graphite calculated is 4.41—6.85nm by its specific surface area. A hydrogen storage and release capacity of 0.33—0.37 weight at room temperature under a modestly high pressure (12MPa) for untreated nano-graphte samples synthesized under different conditions. Under the same condition, the capacity of hydrogen storage and release of untreated carbon nanofibers、multi walled carbon nanotubes and superactive carbon is 0.15wt%—0.35wt％，0.15wt%—0.20wt％，0.92wt%—0.98wt％，respectively.The specific surface area of carbon nanostructured materials is the most important factor in its hydrogen storage and release.
On the stability of the difference scheme in the self-memorization model
Authors: Feng Guo-Lin  , Dong Wen-Jie  , Li Jian-Ping  , Chou Ji-Fan  ,   (1)国家气候中心，北京 100081; (2)兰州大学大气科学系，兰州 730000; (3)扬州大学物理科学与技术学院，扬州 225009;中国科学院大气物理研究所，北京 100029; (4)中国科学院大气物理研究所，北京 100029
Published: December 2020

In light of irreversibility of atmospheric motion, the memory function obtained by utilizing the previous information fully obtained from the observational data is introduced. The selfmemorization equation of the heat conduction equation is induced, and the stability and characteristics of which are studied, taking respectively Richardson scheme (RS) and DuFort-Frankel scheme (DS) as the retrospective order p=1. The calculation results indicate that the numerical integral is diffused sometimes in the multi-time model, due to the fact that the memory function is determined by the observational data via the special mathematics arithmetic, which makes the difference scheme designed previously change, and is a smooth time factor in itself.
Dirac radiation of Vaidya-Bonner-de Sitter black hole
Authors: Shi Wang-Lin  , Liu Xing-Ye  , Liu Zhen-Xing  ,   (1)中国科学院空间科学与应用研究中心，北京 100080; (2)重庆三峡学院电子工程系，万州 404000
Published: December 2020

Dirac equation near horizons of Vaidya-Bonner-de Sitter black hole is discussed. Its Hawking temperature and radiation spectrum are calculated accurately. At the same time, the equation of event horizon is given, which is consistent with the result calculated by zero-curve equation.
Entropy of Dirac field in toroidal black hole
Authors: Wang Bo-Bo  ,   北京交通大学物理系，北京 100044
Published: December 2020

The entropies of quantum fields on event horizon of a toroidal black hole are given using the improved brick-wall model. According to the view of the improved brick-wall model, these entropies are nothing but the entropy of the black hole. So the entropy of the toroidal black hole is proportional to the area of event horizon, which satisfies the Bekenstein-Hawking formula.
Form invariance and Hojman conserved quantity for nonholonomic mechanical systems
Authors: Luo Shao-Kai  , Guo Yong-Xin  , Mei Feng-Xiang  ,   (1)北京理工大学理学院，北京 100081; (2)辽宁大学物理系，沈阳 110036; (3)浙江理工大学数学力学与数学物理研究所，杭州 310018;长沙大学数学力学与数学物理研究所，长沙 410003
Published: December 2020

A non-Noether conserved quantity, i.e. Hojman conserved quantity，constructed by using a form invariance for the nonholonomic mechanical systems is presented. Under special infinitesimal transformations in which the time is not changed, the determining equations of the special form invariance, the constrained restriction equations, the additional restriction equations, and the definitions of the weak form invariance and the strong form invariance of the nonholonomic mechanical systems are given. The condition under which the special form invariance is a special Lie symmetry are obtained. From the special form invariance, the Hojman conserved quantity of the corresponding holonomic systems, the weak Hojman conserved quantity and the strong Hojman conserved quantity of the nonholonomic systems are obtained. And two examples are given to illustrate the application of the result.
Sub-choking phenomenon of low-speed gas flow in a long-constant-area microchannel
Authors: Ding Ying-Tao  , He Feng  , Yao Zhao-Hui  , Shen Meng-Yu  , Wang Xue-Fang  ,   清华大学工程力学系,北京 100084
Published: December 2020

The study on gas flow characteristics in a long-constant-area microchannel in mixed Kn-regime flows has not only theoretical meaning, but also important application in controlling the system of outer space aerocrafts. Flow characteristics were studied based on experiments and approximate theoretical analysis. The inlet pressure was 130, 250 and 320?kPa, and the outlet pressure ranged from 9 to 100?kPa. Five pressure measuring points were distributed along the microchannel and the temperature sensors were located at the inlet and outlet. The pressure distribution and the volume flow rate of air were measured experimentally. An approximate theoretical model based on Poiseuille flow was adopted. Experimental investigations with the long-constant-area microchannel indicate that the mass flow rate through the microchannel changes little as the inlet-to-outlet pressure ratio reaches a certain critical value. The phenomenon is defined as sub-choking and the corresponding pressure ratio is defined as the sub-choking-critical-pressure-ratio. The phenomenon of sub-choking is due to the surface effects. Moreover, the effects of the ratio of surface to volume on the critical pressure ratio are studied.
Extended hyperbolic function method and new exact solitary wave solutions of Zakharov equations
Authors: Huang Ding-Jiang  , Zhang Hong-Qing  ,   大连理工大学应用数学系，大连 116024
Published: December 2020

With the aid of symbolic computation system Maple and by using the extended hyperbolic function method, the exact solitary wave solutions of Zakharov equations are obtained which include bell-shaped soliton solutions, kink-shaped soliton solutions, envelop soliton solutions, singular soliton solutions and a new type of soliton solutions. The method can be also used to solve other nonlinear wave equations.