Effect of electron-electron interaction on polarization process of exciton and biexciton in conjugated polymer

By using one-dimensional tight-binding model modified to include electron-electric field interaction and electron-electron interaction,we theoretically explore the polarization process of exciton and biexciton in cis-polyacetylene.The dynamical simulation is performed by adopting the non-adiabatic evolution approach.The results show that under the effect of moderate electric field,when the strength of electron-electron interaction is weak,the singlet exciton is stable but its polarization presents obvious oscillation.With the enhancement of interaction,it is dissociated into polaron pairs,the spin-flip of which can be observed through modulating the interaction strength.For the triplet exciton,the strong electron-electron interaction restrains its normal polarization,but it is still stable.In the case of biexciton,the strong electron-electron interaction not only dissociate it,but also flip its charge distribution.The yield of the possible states formed after the dissociation of exciton and biexciton is also calculated.

Coexistence of antiferromagnetism and unconventional superconductivity in a quasi-one-dimensional flat-band system:Creutz lattice

We study the coexistence of antiferromagnetism and unconventional superconductivity on the Creutz lattice which shows strictly flat bands in the noninteracting regime.The famous renormalized mean-field theory is used to deal with strong electron-electron repulsive Hubbard interaction in the effective low-energy t-J model,the superfluid weight of the unconventional superconducting state has been calculated via the linear response theory.An unconventional superconducting state with both spin-singlet and staggered spin-triplet pairs emerges beyond a critical antiferromagnetic coupling interaction,while antiferromagnetism accompanies this state.The superconducting state with only spin-singlet pairs is dominant with paramagnetic phase.The A phase is analogous to the pseudogap phase,which shows that electrons go to form pairs but do not cause a supercurrent.We also show the superfluid behavior of the unconventional superconducting state and its critical temperature.It is proven directly that the flat band can effectively raise the critical temperature of superconductivity.It is implementable to simulate and control strongly-correlated electrons'behavior on the Creutz lattice in the ultracold atoms experiment or other artificial structures.Our results may help the understanding of the interplay between unconventional superconductivity and magnetism.

Electron-Electron Collision Term Describing the Reflections Induced Scattering in a Magnetized Plasma

For an electron-electron collision with characteristic scale length larger than the relative gyro-radius of the two colliding electrons, when the initial relative parallel kinetic energy cannot surmount the Coulomb repulsive potential, reflection will occur with interchange of the parallel velocities of the two electrons after the collision. The Fokker–Planck approach is employed to derive the electron collision term C_R describing parallel velocity scattering due to the reflections for a magnetized plasma where the average electron gyro-radius is much smaller than the Debye length but much larger than the Landau length. The electron parallel velocity friction and diffusion coefficients due to the reflections are evaluated, which are found not to depend on the electron perpendicular velocity. By studying the temporal evolution of the H quantity due to CR, it is found that C_R eventually makes the system relax to a state in which the electron parallel velocity distribution is decoupled from the perpendicular velocity distribution.

Evaluation of electron-electron interactions in coupled quantum dots by using far-infrared spectra

We have studied the far-infrared spectra of two-electron vertically coupled quantum dots in an axial magnetic field by exact diagonalization. The calculated results show an obvious difference in role between the interactions for spin S = 1 and for spin S = O. The results support the possibility to evaluate the interactions by far-infrared spectroscopy in vertically coupled quantum dots.

Controlling Three-Dimensional Electron-Electron Correlation via Elliptically Polarized Intense Laser Field

The three-dimensional electron-electron correlation in an elliptically polarized laser field is investigated based on a semiclassical model. Asymmetry parameter α of the correlated electron momentum distribution is used to quantitatively describe the electron-electron correlation. The dependence of α on elliptieity e is totally different in three directions. For the z direction （maJor polarization direction）, α first increases and reaches a maximum at ε = 0.275, then it decreases quickly. For the y direction in which the laser field is always absent, the ellipticity has a minor effect, and the asymmetry parameter fluctuates around α = -0.15. However, for the x direction （minor polarization direction）, α increases monotonously with ellipticity though starts from the same value as in the y direction when ε = 0. The behavior of α in the x direction actually indicates a transformation from the Coulomb interaction dominated correlation to the laser field dominated correlation. Therefore, our work provides an efficient way to control the three-dimensional electron electron correlation via an elliptically polarized intense laser field.

Phonon Mediated Electron-Electron Scattering in Metals

It is shown that the linear resistivity dependence on temperature for metals above the Debye’s temperature mainly is caused by electron-electron scattering of randomly moving electrons. The electron mean free path in metals at this temperature range is in inverse proportion to the effective density of randomly moving electrons, i.e. it is in inverse proportion both to the temperature, and to the density-of-states at the Fermi surface. The general relationships for estimation of the average diffusion coefficient, the average velocity, mean free length and average relaxation time of randomly moving electrons at the Fermi surface at temperatures above the Debye’s temperature are presented. The effective electron scattering cross-sections for different metals also are estimated. The calculation results of resistivity dependence on temperature in the range of temperature from 1 K to 900 K for Au, Cu, Mo, and Al also are presented and compared with the experimental data. Additionally in temperature range from 1 K to 900 K for copper, the temperature dependences of the mean free path, average diffusion coefficient, average drift mobility, average Hall mobility, average relaxation time of randomly moving electrons, and their resultant phonon mediated scattering cross-section are presented.

熔渣规则溶液模型及其在冶金物化中的应用(一)

Lumsden于1961年提出的熔渣规则溶液模型近年得到逐渐发展和完善。作者系统综述了熔渣规则溶液模型及熔渣规则溶液模型中的两个关键多数：阳离子间交互作用能和规则溶液与真实溶液活度转化因子的确定方法。简单介绍了阳离子间交互作用能与二元复合氧化物生成热、阳离子半径的关系。

中美战略竞争的逻辑与前景

随着中国经济持续快速发展和美国经济长期低速增长,美国逐步改变了对中国的认知并几次调整对华政策,中美关系逐渐进入战略竞争阶段。中美战略竞争是美国主动挑起并不断推进对华敌视政策的结果,而根本动因在于战略预阻,即美国预先阻止出现中国对其霸权地位的挑战,但不同时期的预阻目标和切入点有所不同。小布什时期,美国的目标是预阻中国成为美国的挑战者,认为中国的“软肋”是台湾问题;奥巴马时期,美国的目标是预阻中国继续提升影响力和动摇美国的霸权地位,认为中国的“软肋”是台湾问题和南海问题;特朗普时期,美国的目标是预阻中国继续扩大影响力并挑战美国的霸权,认为中国的“软肋”是台湾问题和对美贸易依赖。中美战略竞争的发展逻辑取决于两国政策互动,21世纪初美国谋求对华战略竞争但被中国的灵活政策化解,2008年全球金融危机之后美国对华战略竞争也因中国积极的应对政策和有效措施未能实现其既定目标,特朗普时期的对华战略竞争使中美激烈博弈延续至今。在四种中美关系发展前景中,中美战略竞争有可能保持在可控范围或失去控制。中国的最佳目标选项是争取使之保持可控,基本思路是以我为主、实力为本、策略为重、聚焦美国、着眼世界。

利用MAFIA软件模拟耦合腔慢波结构的冷测特性

利用MAFIA软件对休斯结构的耦合腔慢波结构的色散特性和耦合阻抗进行了模拟,同实验数据相比,其计算精度是令人满意的,从而为耦合腔行波管的生产和研发提供了一个便捷而有力的工具。

Nd-Fe-B永磁合金的微结构和晶粒相互作用

本文介绍了Ｎｄ２Ｆｅ１４Ｂ相的晶格结构及内禀磁性，概述了Ｎｄ－Ｆｅ－Ｂ永磁体的微结构和晶粒相互作用。磁体微结构包括晶粒尺寸、取向和结构缺陷。晶粒相互作用可区分为长程静磁相互作用及近邻晶粒的交换耦合相互作用。我们分析了微结构和相互作用的关系及其对磁体性能的影响，最后介绍了具有发展前景的纳米交换耦合双相复合永磁材料。

荷能离子团簇与介质的相互作用

本文简略介绍在ＭｅＶ量级离子微团簇与介质相互作用领域，我们近年取得的主要成果及意义，实验装置、技术特点、发展方向及应用．

准一维有机铁磁体中的位间电子-电子相互作用

利用扩展的Hubbard模型,对具有链间耦合的准一维有机铁磁链系统的稳定性进行了研究。结果表明,最近邻格点间电子Coulomb排斥相互作用的加强将削弱系统高自旋铁磁性基态的稳定性;电子-声子耦合相互作用与最近邻格点间电子Coulomb排斥相互作用对稳定系统的高自旋铁磁性基态起着不同的作用;系统内的第三近邻电子跳跃相互作用与最近邻格点间电子Coulomb排斥相互作用之间存在着竞争。此外,对系统中的电荷密度和自旋密度分布受最近邻格点间电子Coulomb相互作用影响情况亦进行了讨论。

“服务型教育体系”与广告专业教学模式创新探索

广告专业招生的激增给高校的广告教学、实践、就业等环节带来多方面的压力,众多高校的广告专业面临着广告教育的定位和品牌塑造的挑战。特别是独立本科学院,如何优化“服务型教育体系”,更好地为地方经济服务已成为热点问题。文章从“服务型教育体系”内涵和独立本科学院特点出发,在广告专业的课程设置、课堂教学方式、实验教学、实践基地建立等方面进行整理、剖析,挖掘了其具有实际价值,为独立本科学院培养广告人才提供坚实可佐证的教学模式。

Effect of disorder on exciton dissociation in conjugated polymers

By using a multi-configurational time-dependent Hartree-Fock （MCTDHF） method for the time-dependent Schrrdinger equation and a Newtonian equation of motion for lattice, we investigate the disorder effects on the dissociation process of excitons in conjugated polymer chains. The simulations are performed within the framework of an extended version of the Su-Schrieffer-Heeger model modified to include on-site disorder, off-diagonal, electron-electron interaction, and an external electric field. Our results show that Coulomb correlation effects play an important role in determining the exciton dissociation process. The electric field required to dissociate an exciton can practically impossibly occur in a pure polymer chain, especially in the case of triplet exciton. However, when the on-site disorder effects are taken into account, this leads to a reduction in mean dissociation electric fields. As the disorder strength increases, the dissociation field decreases effectively. On the contrary, the effects of off-diagonal disorder are negative in most cases. Moreover, the dependence of exciton dissociation on the conjugated length is also discussed.

Three-Electron Quantum Dots in Zero Magnetic Field

By using the exact diagonalization method,a system of three electrons confined in a parabolic quantumdot in zero magnetic field is studied.The ground-state electronic structures and orbital and spin angular momentatransitions as a function of the confined strength are investigated.We find that the confinement may cause accidentaldegeneracies between levels with different low-lying states and the inversion of the energy values.The present,resultsare useful to understanding the optical properties and internal electron-electron correlations of quantum dot materials.

Anomalous Hall effect in ferromagnetic Weyl semimetal candidate Zr1-x VxCo1.6Sn

We grew single crystals of vanadium-substituted,ferromagnetic Weyl semimetal candidate Zr1-xVxCo1.6Sn from molten tin flux.These solid solutions all crystallize in a full Heusler structure(L21)while their Curie temperatures and magnetic moments are enhanced by V-substitution.Their resistivity gradually changes from bad-metal-like to semiconductor-like with increasing x while the anomalous Hall effect(AHE),which can be well fitted by Tian-Ye-Jin(TYJ)scaling,[1]is also enhanced.Moreover,we find an apparent electron-electron interaction(EEI)induced quantum correction in resistivity at low temperature.The anomalous Hall conductivity(AHC)dominated by the intrinsic term is not corrected.

Relativistic multichannel treatment of autoionization Rydberg series of 4s^2nf(n=4-23)J~π=(7/2)° for scandium

Based on relativistic multichannel theory, this paper calculates the energy levels of autoionization Rydberg series 4s^2nf（n=4- 23）J^π -（7/2）° of scandium at different levels of approximation within the framework of multichannel quantum defect theory. The present results show that the dipole polarizations play an important role. Considering the dynamical dipole polarization effects, this paper finds that the difference between calculated and experimental quantum defects for the 4s^2nf（n=4- 23）J^π -（7/2）° series is generally about 0.01- 0.03. Furthermore, the reason that 4s^216f is obscured in experimental spectra is suggested to be the interaction with the neighbouring resonance state converged to 3d^2（^1G4） of Sc^＋.

The energy levels of a two-electron two-dimensional parabolic quantum dot

This paper studies the two-electron total energy and the energy of the electron-electron interaction by using a variational method of Pekar type on the condition of electric-LO-phonon strong coupling in a parabolic quantum dot. It considers the following three cases： 1） two electrons are in the ground state; 2） one electron is in the ground state, the other is in the first-excited state; 3） two electrons are in the first-excited state. The relations of the two-electron total energy and the energy of the electron-electron interaction on the Coulomb binding parameter, the electron-LO-phonon coupling constant and the confinement length of the quantum dot are derived in the three cases.

基于概率潮流的电动汽车充放电负荷参与源荷互动策略

伴随着大规模电动汽车和可再生能源发电接入主动配电网,给电网带来诸多不确定性因素,给系统稳定运行造成一定影响。为了应对风电的波动性,研究提出通过价格信号引导电动汽车有序充放电的调度策略。研究首先,建立以电网调度成本期望值最小为目标函数,以调度电动汽车充放电负荷平抑风电波动为约束条件的源荷互动模型,采用粒子群算法求解最优电价下的充放电负荷;然后,计及电动汽车充放电负荷响应风电波动的不确定性,分析电动汽车充放电负荷不确定性对配电网潮流的影响,采用半不变量法计算主动配电网概率潮流;最后用34节点算例进行仿真验证。仿真结果表明,基于源荷互动的有序充放电策略,能够平衡风电功率波动,改善配网电压的波动水平,有利于提高系统运行的稳定性。