在耦合晶格模型中使用反对称立方映象的时空动力学行为

本文首次在耦合映象晶格模型中使用了反对称立方映象，研究了该映象的一般非线性现象。同时较详细地研究了耦合后分岔、周期和混沌等复杂的时空动力学行为。

一类耦合超晶格系统中的电子局域态(英文)

理论研究了一类耦合超晶格系统中的电子局域态 ,该系统是由两个半无限 Ga As/Al As超晶格通过隔离层 Aly Ga1-y As耦合而成 .数值计算表明 y=1时系统仍存在局域态 ,但要求隔离层的厚度比规则垒层的厚度小许多 .比较了只有一个阱层厚度不规则的不规则超晶格系统的局域态和耦合超晶格中局域态的区别 ,发现后者存在两支局域模 ,分别对应于偶宇称态和奇宇称态 ,而在相同参数下 ,前者仅存在偶宇称态 .

KMgF_3∶Mn^(2+)晶体自旋晶格-耦合系数的理论研究

在晶体场理论的强场图象下 ,建立了轴对称 (三角和四角 )晶场中 3d5离子零场劈裂D因子的四阶微扰公式 ,进而得出相应的自旋 晶格耦合系数G11和G4 4.并将上述公式应用于KMgF3 ∶Mn2 + 晶体 ,在不引入调节参量的情况下 ,得到的计算值G11和G4 4与实验结果符合较好 .

卤素桥接混合价含金属络合物中的对角与非对角电子—晶格耦合(英文)

本文研究准一维卤素桥接混合价含过渡金属络合物(HMMC's)中的对角和非对角电子—晶格耦合.利用Green函数方法首次计算了非对角电子—晶格耦合对极化子结合能的影响.结果表明,当同时包括对角和非对角耦合时,这种物质的基态将是电荷密度波(CDW)和键序波(BOW)共存,而以前的研究者都认为在这种物质中只存在电荷密度波(CDW).

含铂准一维卤素桥接混合价络合物(HMPC’S)中的电子——晶格耦合

本文详细研究了含铂准一维卤素桥接混合价络舍物(HMPCS)中电子——晶格(e—p)耦合的对角部分和非对角部分对极化子结合能的影响,证实了在这类物质中,e—p耦合的对角部分是主要的,与实验事实符合。图2,参10。

耦合反对称立方映象晶格中的时空混沌与控制

将反对称立方映象用于耦合晶格之中,着重讨论了这一系统中的时空混沌花样以及混沌控制的普适方法.

两耦合半无限超晶格中的局域界面声子-极化激元

采用转移矩阵方法,研究了含结构缺陷层的两耦合半无限超晶格(GaAs/AlAs)中的局域界面声子-极化激元模性质.研究发现,含不同介电特性的缺陷超晶格结构中的局域界面声子-极化激元模在剩余射线区[ωTO,ωLO]的分布情况与数量存在不同,而且反对称模表现出不同的特征.文中着重研究了缺陷层介电常数与角频率无关的缺陷超晶格,发现该结构中的局域界面声子-极化激元模对组分层的排列顺序与厚度、缺陷层的厚度以及横向波数有着不同程度的依赖.

飞秒激光烧蚀镍的数值模拟

为了研究金属镍的飞秒脉冲激光烧蚀特性,利用三维双温模型和采用有限差分法,对飞秒激光烧蚀镍的三维温度场进行数值模拟,计算得到了单脉冲烧蚀阈值、单脉冲烧蚀半径及烧蚀深度等。通过改变激光能量,研究了电子晶格耦合时间随脉冲能量变化的规律以及脉冲能量对烧蚀半径、烧蚀深度、烧蚀速率的影响。模拟结果表明,随着飞秒脉冲激光能量的增加,材料烧蚀引起的喷射出现的越早,完成烧蚀所用时间越长,烧蚀速率越大,同时材料烧蚀孔半径、深度增加,最终趋于饱和。

Abnormality of Magnetic Behavior and Resistivity of La_(0.7-x)Dy_x Sr_(0.3)MnO_3 (0.00≤x≤0.30)System at Low Temperature

By measuring M-T curves, ρ-T curves and MR-T curves of the samples under different temperatures, the influence of Dy doping （0.00 ≤ x ≤0.30） on the magnetic and electric properties of La0.7-xDyxSr0.3MnO3 has been studied. The experimental results show that, with the increase of the Dy content, the system undergoes a transition from long range ferromagnetic order to the cluster-spin glass state and further to antiferromagnetic order. For the samples with x=0.20 and 0.30, their magnetic behaviors are abnormal at low temperature, and their resistivities at low temperature have a minimum value. These peculiar phenomena not only come from the lattice effect induced by doping, but also from extra magnetic coupling induced by doping.

一种控制时空混沌的方法

本文讨论了反对称立方映象的Ｌｙａｐｕｎｏｖ指数，提出了一种控制耦合映象晶格中时空混沌的新方法。

Superlattice Patterns in Coupled Turing Systems

In this paper, superlattice patterns have been investigated by using a two linearly coupled Brusselator model. It is found that superlattice patterns can only be induced in the sub-system with the short wavelength. Three different coupling methods have been used in order to investigate the mode interaction between the two Turing modes. It is proved in the simulations that interaction between activators in the two sub-systems leads to spontaneous formation of black eye pattern and/or white eye patterns while interaction between inhibitors leads to spontaneous formation of super-hexagonal pattern. It is also demonstrated that the same symmetries of the two modes and suitable wavelength ratio of the two modes should also be satisfied to form superlattice patterns.

A Cryptographic Scheme Based on Spatiotemporal Chaos of Coupled Map Lattices

We propose a cryptographic scheme based on spatiotemporal chaos of coupled map lattices （CIVIL） ,which is based on one-time pad. The structure of the cryptosystem determines that the progress in decryption implies the progress in exploring the dynamical behavior of spatiotemporal chaos in CML. A part of the initial condition of CML is used as a secret key, and the recovery of the secret key by exhaustive search is impossible due to the sensitivity to the initial condition in spatiotemporal chaos system. Specially the software implementation of the scheme is easy.

Impact of a background velocity field on solidification growth of single-crystal nuclei using the PF-LBM

To promote/inhibit ice formation in the natural environment and industrial systems,the growth and evolution process of ice single-crystal nuclei were simulated using the phase field-lattice Boltzmann method(PF-LBM),and the influence of a background flow field on the growth of single-crystal nucleus dendrites was also analyzed.The results show that the flow field makes dendrite growth asymmetric.The growth of dendrites is more developed on the upstream side than on the downstream side.The dendrite tip growth rate and tip radius are greater on the upstream side than on the downstream side.The solid phase ratio is greater with a background flow field than without one.The higher the flow velocity is,the more developed the dendrites on the upstream side,the faster the dendrites grow,and the higher the dendrite tip growth rate.The dendrites on the backflow side have a lower flow rate and a lower degree of supercooling than those on the upstream side,which inhibits the solidification process,the growth rate is slow,and the dendrites are underdeveloped.

(2+2)-Dimensional Discrete Soliton Equations and Integrable Coupling System

In this paper, we extend a （2＋2）-dimensional continuous zero curvature equation to （2＋2）-dimensional discrete zero curvature equation, then a new （2＋2）-dimensional cubic Volterra lattice hierarchy is obtained. Fhrthermore, the integrable coupling systems of the （2＋2）-dimensional cubic Volterra lattice hierarchy and the generalized Toda lattice soliton equations are presented by using a Lie algebraic system sl（4）.

Phase Diagram of XY Model with Nematic Coupling on the Simple Cubic Lattice

Using cluster Monte Carlo method, we numerically investigate the coupling on the simple cubic lattice. We determine critical lines belong to the criticality in the XY model with nematic three-dimensional XY universality class in variable of θ （2θ） between the XY-ferromagnetic （nematic） and disordered states. Fhrthermore, the phase transition between the XY-ferromagnetic and the nematie states is found to be in the three-dimensional Ising universality class. The critical points are determined from the intersections of Binder ratios for various system sizes. With two sets of critical points obtained, we finally construct the phase diagram on the A-J plane.

Effects of Thermal Lattice Vibration on the Effective Potential of Weak-Coupling Bipolaron in a Quantum Dot

Based on the Huybrechts' linear-combination operator,effects of thermal lattice vibration on the effective potential of weak-coupling bipolaron in semiconductor quantum dots are studied by using the LLP variational method and quantum statistical theory.The results show that the absolute value of the induced potential of the bipolaron increases with increasing the electron-phonon coupling strength,but decreases with increasing the temperature and the distance of electrons,respectively;the absolute value of the effective potential increases with increasing the radius of the quantum dot,electron-phonon coupling strength and the distance of electrons,respectively,but decreases with increasing the temperature;the temperature and electron-phonon interaction have the important influence on the formation and state properties of the bipolaron:the bipolarons in the bound state are closer and more stable when the electron-phonon coupling strength is larger or the temperature is lower;the confinement potential and coulomb repulsive potential between electrons are unfavorable to the formation of bipolarons in the bound state.

The Phase Transition during Post Annealing

We have studied why PA （post-annealing） takes a long time to restore damaged crystallinity, which corresponds to repeat 10 10 times of lattice vibrations. Using a MD （molecular dynamics） simulation, we monitored the time-series of the LRO （long-range order） parameter as LRO pattern, in the case of a type IIa diamond, from the beginning of ion impact by a sub-keV N2 beam implantation to a few nanoseconds, i.e., close to the feasible time limit for MD simulations. Due to the ion impact, the LRO parameter changed gradually from ＂LRO = 1＂ （crystal） to ＂LRO = 0＂ （amorphous）, showing the so-called critical slowing-down phenomenon. However, since PA was started the LRO pattern was not unique. The LRO patterns were grouped into more than three types of phases and the transition between them was also found. From the viewpoint of statistical dynamics, such chaotic variations in the LRO pattern may present that the system is a GCM （globally coupled map） of a complex system in a closed system. A GCM composed of coupled oscillators develops slowly to exhibit several different phases or ‘chaotic itinerancy＇ over time. Therefore, the long duration required for PA may be attributable to the nature of a complex system.

Specific Heat of a Two-Layer Magnetic Superlattice

The specific heats of both a two-layer ferromagnetic superlattice and a two-layer ferrimagnetic one arestudied.It is found that the spin quantum numbers,the interlayer and intralayer exchange couplings,the anisotropy,theapplied magnetic field,and the temperature all affect the specific heat of these superlattices.For both the ferromagneticand ferrimagnetic superlattices,the specific heat decreases with increasing the spin quantum number,the absolutevalue of interlayer exchange coupling,intralayer exchange coupling,and anisotropy,while it increases with increasingtemperature at low temperatures.When an applied magnetic field is enhanced,the specific heat decreases in the two-layerferromagnetic superlattice,while it is almost unchanged in the two-layer ferrimagnetic superlattice at low fieldrange at low temperatures.

Magnetoelastic Instability in Ring-Shaped Molecule Magnets with Next-Nearest Neighbor Coupling

In considering next-nearest neighbor （NNN） coupling, we numerically investigate the magnetoelastic instability in ring-shaped mesoscopic antiferromagnetic Heisenberg spin 1/2 systems with spin-phonon interaction. The results indicate that, for antiferromagnetic NNN coupling J2, there may be a critical value J2^c, at which the ground state is dimerized for arbitrary lattice spring constant and beyond and below which the magnetoelastic instability behavior is different from each other. The values of J2^c are irrelevant to the system size. For ferromagnetic NNN coupling, only continuous transition is present from dimerized phase to uniform phase as lattice spring constant is increased.

稀土单分子磁体研究进展

单分子磁体是一类纳米尺度的磁性材料,在高密度信息存储、量子比特和自旋电子器件等方面具有潜在的应用价值而备受关注。由于稀土离子具有大的磁矩和强的磁各向异性,稀土离子在高性能单分子磁体构筑方面有过渡金属离子不可比拟的优势。近年来,以单核和双核稀土单分子磁体为代表的稀土单分子磁体的研究取得了长足的进展,尤其是突破了以液氮沸点温度(77 K)为界限的磁阻塞温度,为室温下的单分子信息存储迈出了坚实的一步。