一维分子晶体模型中立方型相互作用引起的孤子激发

得到考虑了立方型相互作用后的一维分子晶体模型的孤子激发的运动解.在忽略了三次项的近似下,孤子激发的运动解回复于通常的极化子解.计算了孤子激发的峰宽和峰值.并指出了孤子激发与通常极化子解的差别.     

螺旋多肽链中的孤子与生物现象

提出一个描述螺旋多肽链的氢键链间耦合模型。得到了扭结团,包络孤子团和呼吸子团。其中对称和非对称扭结团分别对应于螺旋多肽链的压缩（或扩张）和扭曲变形区。     

有色散项的一维分子晶体模型的孤子激发

本文得到了考虑了色散项后的一维分子晶体模型的孤子激发的运动解,在忽略了色散项的近似下,此运动解回复于通常极化子解。计算了模型中运动的自隐态的晶格位移,电子的自陷阱和电流密度以及孤子激发的峰值,峰宽,有效质量和束缚能以及Ｂｌｏｃｈ能带底部电子的的能量。     

非局域非线性介质中一个耦合系统的时空光孤子解

多维(2维和3维)孤子在光学中引起了许多人的关注,最重要的3维时空孤子常被称作"光弹". 已有结论证明了非局域非线性介质中一个耦合系统存在稳定3维时空孤子.应用一个辅助常微分方程,借助Maple软件,求得这个系统的时空光孤子解.结果表明,这个系统存在不同形式的包络孤子解.     

非局域耦合带有自PT对称Schrdinger方程的N重达布变换

目前,关于非线性薛定谔方程的研究工作取得了巨大的成果,然而对于PT对称的非局域耦合薛定谔方程所做的研究比较少.主要研究非局域耦合薛定谔方程,我们从3×3 Lax对出发,利用达布变换的方法,得到新解与旧解之间的关系.经过复杂的计算,得到1-孤子解,2-孤子解以及N-孤子解计算公式.最后,利用画图软件,得到一些孤子演化图,其中包括亮孤子波解,呼吸波解和怪波.同时,显示了两孤子之间的弹性相互碰撞,它们的振幅在相互作用后,除了相移之外保持不变.     

一维非线性单原子分立晶格振动的格孤波解和非传播呼吸子解

利用多重尺度方法和准分立方法，对一维非线性单原子分立晶格的振动方程进行求解，得到了其在布里渊区中心处和布里渊区边界上具有非传播的呼吸子解，而在晶格的其它处具有传播的包络孤子，亦即格孤波解。     

非局域非线性介质中一个耦合系统的精确解

在光学中研究多维（二维和三维）孤子引起了许多学者的关注,最重要的三维时空孤子时常被称作“光弹”．D．Mihalache等证明了非局域非线性介质中一个耦合系统存在稳定三维时空孤子．文章应用试探函数法,借助Maple软件,求得这个系统的时空光孤子解和周期解．结果表明,这个系统存在不同形式的包络孤子解和周期解．     

顺式聚乙炔中极化子电子态的研究

本文在反式聚乙炔分立模型的基础上,考虑到顺式聚乙炔中的孤子对间存在着吸引力.引入孤子对间的禁闭势,作为顺式聚乙炔的分立模型.对顺式聚乙炔中极化子的电子态的研究发现:电子晶格耦合常数λ=0.4,对不同的禁闭参数r.在导带、价带的顶部或底部存在四个新的电子局域态;λ=0.25,对不同的禁闭参数,能隙中的二个新的局域态不出现.它们均为浅局域态.本文结果支持了最近发现孤子新的电子局域态的结果.本文方法可推广到基态具有非简并的类似系统.     

最近邻作用项对一维分子链孤子激发的影响

在电-声相互作用的一维分子晶体中,电子不仅与在位格点上的声子有相互的作用,同时与近邻格点也存在着微弱的相互作用.为了更真实地求解出一维分子晶体系统的基态问题,以量子化Holstein模型为基础并考虑电子与最近邻格点上声子的相互作用项对其的修正,此时系统处于基态时的Hamiltonian量也发生了相应的改变.运用压缩-相干态展开法和能量极小值等原理,求解出处于基态时极化子系统所满足的非线性Schrdinger方程和对应的孤子解、基态能量.并讨论了最近邻作用项的强度对一维分子链孤子激发如孤子的波峰、波宽、稳定性和系统基态能量的影响.     

(2+1)维呼吸子的可视化研究

呼吸子是一种特殊的局域振荡孤子。用可视化的方法研究(2+1)维Nizhnik-Novikov-Veselov方程的静态呼吸子和运动反呼吸子,直观地再现(2+1)维呼吸子丰富的特性,是对(2+1)维呼吸子研究方法的拓展。     

Unusual phase transitions in ferroelectric nanodisks and nanorods

Bulk ferroelectrics undergo structural phase transformations at low temperatures, giving multi-stable (that is, multiple-minimum) degenerate states with spontaneous polarization. Accessing these states by applying, and varying the direction of, an external electric field is a key principle for the operation of devices such as non-volatile ferroelectric random access memories (NFERAMs). Compared with bulk ferroelectrics, low-dimensional finite ferroelectric structures promise to increase the storage density of NFERAMs 10,000-fold. But this anticipated benefit hinges on whether phase transitions and multi-stable states still exist in low-dimensional structures. Previous studies have suggested that phase transitions are impossible in one-dimensional systems, and become increasingly less likely as dimensionality further decreases. Here we perform ab initio studies of ferroelectric nanoscale disks and rods of technologically important Pb(Zr,Ti)O3 solid solutions, and demonstrate the existence of previously unknown phase transitions in zero-dimensional ferroelectric nanoparticles. The minimum diameter of the disks that display low-temperature structural bistability is determined to be 3.2 nm, enabling an ultimate NFERAM density of 60 x 10(12) bits per square inch-that is, five orders of magnitude larger than those currently available. Our results suggest an innovative use of ferroelectric nanostructures for data storage, and are of fundamental value for the theory of phase transition in systems of low dimensionality.     

Room-temperature ferroelectricity in supramolecular networks of charge-transfer complexes

Materials exhibiting a spontaneous electrical polarization that can be switched easily between antiparallel orientations are of potential value for sensors, photonics and energy-efficient memories. In this context, organic ferroelectrics are of particular interest because they promise to be lightweight, inexpensive and easily processed into devices. A recently identified family of organic ferroelectric structures is based on intermolecular charge transfer, where donor and acceptor molecules co-crystallize in an alternating fashion known as a mixed stack: in the crystalline lattice, a collective transfer of electrons from donor to acceptor molecules results in the formation of dipoles that can be realigned by an external field as molecules switch partners in the mixed stack. Although mixed stacks have been investigated extensively, only three systems are known to show ferroelectric switching, all below 71 kelvin. Here we describe supramolecular charge-transfer networks that undergo ferroelectric polarization switching with a ferroelectric Curie temperature above room temperature. These polar and switchable systems utilize a structural synergy between a hydrogen-bonded network and charge-transfer complexation of donor and acceptor molecules in a mixed stack. This supramolecular motif could help guide the development of other functional organic systems that can switch polarization under the influence of electric fields at ambient temperatures.     

High Resolution Acoustic Microscopy with Low Frequency and Its Applications in Analysis of Ferroelectrics

Ferroelectrics have spontaneous polarization, which can be oriented along with electric field and show high dielectric constant, high switching speed, nonvolatile memory character and large capacity memories on a given silicon wafer. Large-scale manufacturing is presently underway to incorporate ferroelectric materials as storage and bypass capacitors in IC circuitry. Nondestructive observation of domain structure of ferroelectrics, dynamic behavior under external field and related phenomena is becoming sig...     

Magnetic phase control by an electric field

The quest for higher data density in information storage is motivating investigations into approaches for manipulating magnetization by means other than magnetic fields. This is evidenced by the recent boom in magnetoelectronics and 'spintronics', where phenomena such as carrier effects in magnetic semiconductors and high-correlation effects in colossal magnetoresistive compounds are studied for their device potential. The linear magnetoelectric effect-the induction of polarization by a magnetic field and of magnetization by an electric field-provides another route for linking magnetic and electric properties. It was recently discovered that composite materials and magnetic ferroelectrics exhibit magnetoelectric effects that exceed previously known effects by orders of magnitude, with the potential to trigger magnetic or electric phase transitions. Here we report a system whose magnetic phase can be controlled by an external electric field: ferromagnetic ordering in hexagonal HoMnO3 is reversibly switched on and off by the applied field via magnetoelectric interactions. We monitor this process using magneto-optical techniques and reveal its microscopic origin by neutron and X-ray diffraction. From our results, we identify basic requirements for other candidate materials to exhibit magnetoelectric phase control.     

双势垒磁性隧道结中电子的自旋极化输运

 采用相干量子输运理论和传递矩阵方法,数值计算了两端具有铁磁接触的双势垒异质结构(F/DB/F)中自旋相关的隧穿几率和自旋极化率。结果表明,隧穿几率和自旋极化率随阱宽的增加发生振荡周期不随垒厚变化的周期性振荡;Rashba自旋轨道耦合强度的增加加大了隧穿几率和自旋极化率的振荡频率;隧穿几率和自旋极化率的振幅和峰谷比强烈依赖于两铁磁电极中磁化方向的夹角。与铁磁/半导体/铁磁（F/S/F）磁性隧道结中的结果相比,发现垒厚的增加增大了隧穿几率和自旋极化率的峰谷比,自旋极化率的取值明显增大,并具有自旋劈裂和自旋翻转现象出现。     

色散补偿光纤中呼吸波周期行为的剖析

沿用近似描述含色散补偿光纤中呼吸波形成与传播机制的一个非自治、二维常微模型 ,讨论此模型中所有可能出现的周期呼吸波 ,按其相空间结构进行分类及全面刻划 ,给出各类呼吸波振幅和周期的一些定性与定量的结果 ,为超高比特率远程通讯光纤的设计提供理论依据     

铁电体的非线性光学效应和电光效应的起因研究

本文从铁电体在外场中的极化入手,不考虑应力场和温度场的作用,即忽略压电效应和热电效应,研究探讨了铁电体的非线性光学效应和电光效应的起因,并对其在新的科技领域的应用作了简单介绍.     

Thermal expansion in lead zirconate titanate

The volume anomalies with temperature variations in tin-modified lead zirconate titanate ceramics are investigated. Experimental results show that the volume changes are related to the phase transitions induced with temperature. The magnitude and orientation of crystal volume changes are dependent on the particular phase transition. When antiferroelectrics is transformed to ferroelectrics or paraelectrics the volume expands. Oppositely when ferroelectrics is transformed to antiferroelectrics or paraelectrics the volume contracts. In the transition of antiferroelectric orthorhombic structure to tetragonal structure or ferroelectric low-temperature rhombohedral structure to high-temperature rhombohedral structure, there are also revealed apparent anomalies in the curves of thermal expansion. Among them, the volume strain caused by the transition between antiferroelectrics and ferroelectrics is the biggest in magnitude, and the linear expansion dL/L₀ and the expansion coefficient (dL/L ₀)/dT can reach 2.8 × 10⁻³ and 7.5 × 10⁻⁴ K⁻¹ respectively.     

钛酸锶钡陶瓷的铁电极化疲劳效应

 用微分电滞回线谱分析方法研究了钛酸锶钡Ba_0.95Sr_0.05TiO₃ （BST）陶瓷圆片的铁电极化疲劳效应,发现其疲劳过程可以分成三个阶段,当反转次数在10⁵-10⁶次时出现老化效应,反转10⁶-10⁸时出现疲劳效应,反转10⁸次以上则样品完全疲劳,铁电性几乎消失。