N-S多层薄膜结构的超导临界温度讨论

本文推广了McMillan隧道模型,并应用于厚度小于超导相干长度的超导和正常膜组成的N-S多层薄膜结构。计算了它的序参量和超导临界温度。由于界面区域电声子作用的修正以及不同原子的掺杂所引起的T_c增强的可能性也作了讨论。 关键词：     

单晶石墨、多晶石墨电导行为的差异

报道了单晶石墨、多晶石墨电导行为的差异.在8.15T磁场下，4.5K处单、多晶石墨的正磁电阻效应分别为69400%，170%，同时在0T，8T磁场作用下，多晶石墨的电导行为呈现类绝缘体型性质，但在单晶石墨中我们发现了与磁场相关的类半金属-绝缘体型转变，通过分析，我们认为：单、多晶石墨电导行为存在较大差异的原因可能来源于库仑相互作用在高定向热解石墨中变得不可忽视，而多晶石墨样品却存在晶界散射. 关键词： 半金属石墨 类半金属-绝缘体型转变     

Spin-Triplet Andreev Reflection in Ferromagnet/Ferromangnet/s-Wave Superconductor Junctions

Four-component Bogoliubov-de Gennes equations are applied to study the tunnelling conductance spectra G（ E） of half-metallic ferromagnet/ferromagnet/s-wave superconductor tunnel junctions. It is found that only for noncollinear magnetizations, there exists nonzero G（ E） structure within the energy gap, which is a signature of appearance of the novel Andreev reflection and spin-triplet pairing correlations.     

Spin-filtering junctions with double ferroelectric barriers

An FS/FE/NS/FE/FS double tunnel junction is suggested to have the ability to inject, modulate and detect the spin-polarized current electrically in a single device, where FS is the ferromagnetic semiconductor electrode, NS is the nonmagnetic semiconductor, and FE the ferroelectric barrier. The spin polarization of the current injected into the NS region can be switched between a highly spin-polarized state and a spin unpolarized state. The high spin polarization may be detected by measuring the tunneling magnetoresistance ratio of the double tunnel junction.     

Unified semiclassical approach to electronic transport from diffusive to ballistic regimes

We show that by integrating out the electric field and incorporating proper boundary conditions,a Boltzmann equation can describe electron transport properties,continuously from the diffusive to ballistic regimes.General analytical formulas of the conductance in D = 1,2,3 dimensions are obtained,which recover the Boltzmann–Drude formula and Landauer–B ¨uttiker formula in the diffusive and ballistic limits,respectively.This intuitive and efficient approach can be applied to investigate the interplay of system size and impurity scattering in various charge and spin transport phenomena,when the quantum interference effect is not important.     

Coupling-matrix approach to the Chern number calculation in disordered systems

The Chern number is often used to distinguish different topological phases of matter in two-dimensional electron systems. A fast and efficient coupling-matrix method is designed to calculate the Chern number in finite crystalline and disordered systems. To show its effectiveness, we apply the approach to the Haldane model and the lattice Hofstadter model, and obtain the correct quantized Chern numbers. The disorder-induced topological phase transition is well reproduced, when the disorder strength is increased beyond the critical value. We expect the method to be widely applicable to the study of topological quantum numbers.     

自旋输运和巨磁电阻--自旋电子学的物理基础之一

介绍磁性纳米结构和锰氧化物中电子的自旋极化输运和巨磁电阻效应，它们是新近发展的自旋电子学的物理基础之一．着重讨论的是以下三方面的基本物理图像：磁多层结构的巨磁电阻，铁磁隧道结的隧穿磁电阻，掺杂锰氧化物的庞磁电阻效应．     

磁通格子的有序-无序相变和反向熔化

考虑了无序钉扎、热涨落和磁通互作用, 用Monte Carlo分子动力学模拟方法研究二维磁通格子在无序钉扎强度和温度空间的相图, 以及由布拉格玻璃相到非晶磁通玻璃相和到磁通液体相的有序-无序相变.为了决定磁通格子的序，计算了静态结构因子和磁通格子位形的有限尺寸指数.计算结果表明，Bragg玻璃相在低温的无序磁通玻璃相和高温的磁通液体相之间 , 表现出磁通格子的反向熔化行为.分析后认为，这一反向熔化行为起因于磁通之间互作用的温度效应. 关键词： Ⅱ类超导体 磁通格子 相图 结构因子 反向熔化     

磁通密度对第Ⅱ类超导体磁通动力学的影响

计算了二维无序钉扎系统中磁通运动的平均速度、微分电阻、纵向电压噪声和静态结构因子.通过在不同磁通密度下的磁通运动形式,给出了磁通运动的动力学相图.研究表明,磁通晶格存在钉扎相、塑性流相、近晶流相,和运动玻璃相.在运动玻璃相中,随着驱动力的进一步增加,横向玻璃态和运动Bragg玻璃态相继出现.磁通密度增大有利于有序相的出现.当磁通密度增大到一定程度时,近晶流动相会消失.磁通运动随着外加驱动电流增大发生从塑性流动相到运动玻璃相的转变 关键词： Ⅱ类超导体 磁通动力学 运动玻璃     

1:3Peierls系统中的极化子

在可约数为3的一维Peierls系统中,我们运用SSH模型的连续极限得到了极化子解。在弱耦合极限下,这一极化子解严格满足离子位移序参量的自洽条件。我们给出了极化子的形成能和特征宽度,并讨论了可约数为M的一般情况下可能的孤子激发。