双杂质一维原子链中的晶格振动

对于含有两个杂质的一维单原子链的振动方程求解,得到晶格振动频率的解.分析了振动频率和杂质质量以及两杂质间距离的关系.     

Aligned Elongation of Ag Nanoparticles Embedded in Silica Irradiated with High Energy Ni Ions

Metallic nanoparticle(NP) shapes have a significant influence on the property of composite embedded with metallic NPs. Swift heavy ion irradiation is an effective way to modify shapes of metallic NPs embedded in an amorphous matrix. We investigate the shape deformation of AgNPs with irradiation fluence, and 357 MeV Ni ions are used to irradiate the silica containing AgNPs, which are prepared by ion implantation and vacuum annealing. The UV-vis results show that the surface plasmon resonance(SPR) peak from AgNPs shifts from 400 to 377 nm. The SPR peak has a significant shift at fluence lower than 1 × 10~(14) ions/cm2 and shows less shift at fluence higher than 1 × 10~(14) ions/cm~2. The TEM results reveal that the shapes of AgNPs also show significant deformation at fluence lower than 1 × 10~(14) ions/cm~2 and show less deformation at fluence higher than1 × 10~(14) ions/cm~2. The blue shift of the SPR peak is considered to be the consequence of defect production and AgNP shape deformation. Based on the thermal spike model calculation, the temperature of the silica surrounding Ag particles first increases rapidly, then the region of AgNPs close to the interface of Ag/silica is gradually heated. Therefore, the driven force of AgNPs deformation is considered as the volume expansion of the first heated silica layer surrounding AgNPs.     

Spin-Flip Process of Polarons in Conjugated Polymers with Magnetic Impurities

Being driven by an external electric field a polaron carrying both spin 1/2 and charge ±e moves at a constant speed in a polymer chain. When the polaron passes through a specific site, which couples to a magnetic impurity via spin-exchange interactions, its spin undergoes a spin-flip process if it is antiparallel to the impurity spin. Our numerical simulation shows that （a） a swap-like operation is performed between the polaron and impurity during the scattering process （b） polarons might be good candidates to be information carriers in the molecular scale.     

含stubs量子波导系统的电子自旋极化输运性质

理论上研究了含stubs的Rashba自旋轨道耦合（spin-orbit coupling, SOC）量子波导系统的自旋极化输运性质. 利用晶格格林函数方法,发现由于stubs和SOC产生的势阱使系统中出现束缚态,这些束缚态与传播态之间相互干涉导致电导中出现Fano共振结构,同时在对应的自旋极化率中也出现Fano共振或反共振结构. 此外,由于系统结构的突变使电子被反向散射和量子干涉效应,电导中出现一系列的共振峰. 但是,当系统加上外磁场后,所有这些效应都被抑制, 系统重新出现量子化电导, 同时自旋电导也出 关键词： 量子波导 自旋极化输运 自旋轨道耦合     

基于类叉形纳米结构的自旋极化电流分离器

采用递归格林函数法研究了含Rashba自旋轨道耦合(spin-orbit coupling,简记SOC)效应的类叉形纳米结构中电子的自旋极化输运性质。结果表明在非自旋极化电子入射时系统的两个出射端能得到大小相等但极化方向相反的两个自旋极化电流,其物理根源是由Rashba SOC和系统的几何结构导致的两出射端具有大小不相等的自旋电导。当系统中引入无序时,无序强度对自旋极化电流的影响较弱。这些效应说明所研究的系统有可能用来设计自旋极化电流分离器。     

准周期对spin-Peierls模型中晶格畸变和能隙的影响

采用严格对角化方法和自洽方法，研究准周期相互作用对spin-Peierls模型中晶格畸变和能隙的影响.研究表明，引入准周期作用后，spin-Peierls模型中晶格畸变和能谱表现出准周期结构的自相似特性.另外，在弹性系数K取不同值时，随着准周期作用强度的增强，晶格畸变的平均值可能会增大、减小或先增大后减小，其对应的能隙也有相似的行为. 关键词： 准周期相互作用 spin-Peierls模型     

具有Dzyaloshinskii-Moriya相互作用的二维spin-Peierls模型的基态行为

在平均场理论基础上,研究了具有DzyaloshinskiiMoriya(缩写为DM)相互作用的二维spinPeierls模型以及DM相互作用对二聚化的影响.研究表明,随模型参量的不同,DM相互作用能加强或削弱二聚化位移.另外,发现DM相互作用对二聚化位移的依赖程度参量λ存在一个特殊点λc,当λ=λc时,DM相互作用对二聚化没有影响.随晶格弹性系数的增加,λc将增大,而链间耦合将使λc减小 关键词： 二维spinPeierls模型 DM相互作用     

Ground—State Properties of a Local Sine—Gordon Model with Two Frequencies

The local sine-Gordon model with two frequencies is studied by a variational method.The renormalization mass and classical field path are calculated.We find an Ising-like phase transition,which is analogous in the global sine-Gordon model with two frequencies.A full phase diagram is given.     

Scaling Properties of Energy Gap in Dimerized Spinless Fermion Chains with Quasiperiodic Modulation

By employing the exact diagonalization method, we investigate the low-energy benavlour ot the almenzed spinless fermion chains with quasiperiodic modulation. It is found that for off-diagonal modulation, the energy gap with length N scales as exp（-cN^ω） with nonuniversal exponent ω if the dimerization is nonzero. However, for diagonal modulation, there may exist a critical dimerization δc beyond which the system exhibits a metal-insulator transition.     

一维扩展离子Hubbard模型的相图研究

应用密度矩阵重整化群方法, 研究了存在交错离子势Δ时一维半满扩展Hubbard模型的相图. 通过计算关联函数、结构因子、位置算符等方法, 描绘了从Mott绝缘体-键有序绝缘体-Band 绝缘体的特性并给出了精确的相边界. 研究发现: 中间的键有序绝缘体相在相图中占据了很小的一部分区域, 当存在离子势Δ的情况下, 这个区域将会有所增大; 而当相互作用足够强时, 这个中间相消失. 给出了离子Hubbard模型(最近邻电子-电子相互作用V=0)的相图.