磁场下高温超导YBCO颗粒膜的非平衡微波响应

应用二维约瑟夫逊弱连接网络模型 ,讨论了磁场引起的二维超导体系中磁通“涡旋反涡旋”束缚对的激发问题 ,给出了自由涡旋分布 n( T,H )的分析表达式 ,对比 YBCO颗粒膜样品的非平衡微波响应测量数据发现 :两者具有相似的分布特征。该结果表明 ,高温超导颗粒膜的非平衡微波响应机制与磁通“涡旋反涡旋”束缚对的激发态可能存在某种内在联系。     

磁场下高温超导YBCO颗粒膜的非平衡微波响应

本文应用二维约瑟夫森弱连接网络模型,讨论了磁场经起的二维超导体系中磁通“涡旋－反涡施“束缚对的激发问题,给出了自由涡旋分布n（T,H）的分析表达式,对比YBCO颗粒膜样品的非平衡微波响应,测量数据发：两者具有相似的分布特征。该结果表明,高温超导颗粒膜的非平衡微波响应机制与磁通“涡旋－反涡旋”束缚对的激发态可能存在某种内在联系。     

高温超导体Josephson阵列在磁场中的微波响应与磁通涡旋激发

本文从分析相变电阻率 ρP 和磁通蠕动电阻率 ρF 出发 ,指出当T小于某一温度T0 时 ,ρF>ρP,而当T >T0 时 ,ρF 远小于 ρP,并进一步分析了 ρF 与 ρP 随温度的变化率分布图 ,得出磁通蠕动电阻率 ρF 随温度的变化率分布图跟微波响应曲线具有相似的分布特征 ,结果表明 :高温超导体的非平衡微波响应机制可能与磁通涡旋的激发有关 .     

YBCO颗粒膜的非平衡微波响应与Koterlitz-Thouless相变

报道了Yba₂Cu₃O_7-δ(YBCO)颗粒膜的微波辐射(λ＝8mm)响应的特征.实验结果表明：YBCO颗粒膜的微波响应行为不能用辐射热效应来描述,而应当属于非平衡响应行为.在超导转变温度T_∞以下温区,非平衡微波响应信号电平随样品电阻R趋于零而消失,并且对弱的外磁场十分灵敏.在对样品的直流I-V特性进行了仔细测量后发现,样品的电输运行为具有准二维结构特征,可以用Kosterlitz-Thouless(K-T)相变模型加以描述.在此基础上,分析结果表明:YBCO颗粒膜中的非平衡微波响应机制可能与磁通“涡旋-反涡旋”束缚对的激发态有关. 关键词：     

高温超导YBCO颗粒膜桥型器件的8mm微波视频检测

在高温超导 YBCO颗粒膜上刻成 0 .3× 0 .1 mm2 的桥型样品 ,测量了它在磁场和微波辐照下的响应特性。实验结果表明 :通过优化器件参数 ,响应率可达 1 0 4V/ W,在 T=70 K时噪声等效功率约为 5.2× 1 0 -1 4 W/ Hz1 / 2 ,当入射微波斩波频率为 50 0 k Hz时 ,响应时间低于 3.9× 1 0 -8s。     

非平衡辐射响应与准二维高温超导体系的磁通涡旋激发

从实验上揭示了高温超导体YBa₂Cu₃O_{7-δ(YBCO)颗粒膜具有准二维结构的输运特征以及超导弱连接行为特征.在此基础上,将超导颗粒膜样品等效为准二维Josephson弱连接阵列系统,讨论了电流引起的二维超导体系中磁通“涡旋-反涡旋”束缚对的拆对激发问题,并给出了自由涡旋分布n(T,I)的分析表达式.将颗粒膜样品的非平衡辐射响应测量结果与电流激发自由涡旋分布n(T,I)相比较,两者具有相似的分布特征.该结果表明,高温超导体颗粒膜 关键词：}     

红外光激发作用下分子导电纳米结的非弹性电流研究

将"金属-单分子-金属"模型化为分子导电纳米结,应用扩展主方程方法研究了红外光激发作用下弱耦合分子导电纳米结的非弹性电流的传导过程.分别采用偶极跃迁的指数耦合、平方耦合以及线性耦合模型描述红外光场与分子的相互作用,研究了不同光场作用下非弹性电流与所加电压的关系,并讨论了分子内振动能重新分布效应对电流-电压特性的影响. 关键词： Franck-Condon阻滞 非弹性电流 电流-电压特性 红外光激发     

飞秒激光作用下全向高反膜破坏的激发过程

设计和制备了全向高反膜SiO₂/TiO₂，研究了它在不同脉冲宽度、不同脉冲能量的飞秒激光作用下的破坏阈值和烧蚀深度.利用发展的抽运-探针方法，研究了抽运脉冲作用下材料中导带电子的超快激发和能量沉积过程，建立并求解了飞秒激光激发材料和材料的激发对抽运光自身反作用的耦合动力学模型.模型较好地揭示了材料破坏的激发过程. 关键词： 飞秒激光 全向高反膜 激发过程 破坏机制     

Effective Response of Nonlinear Spherical Coated Composites Under External AC and DC Electric Field

Under the external AC and DC electric field, the effective response of nonlinear spherical coated composites, which obey the constitutive relation of electric displacement and electric field, is investigated in the dilute limit by using the perturbation method. The local potentials in inclusion and host regions are derived at all harmonics. Moreover, the formulae of the effective linear and nonlinear responses are given in the dilute limit.     

Spin-Dependent Scattering and Giant Magnetoresistance in Magnetic Granular Films

Based on a macroscopic theory in which the spin-dependent interface scattering and the bulk scattering are included, the transport properties in systems of cylindrical magnetic granules are investigated analytically. It is shown that the giant magnetoresistance as well as the resistivities of these systems depend strongly on the size of the granules.     

Effective Response of Nonlinear Composite under External AC and DC Electric Field

A perturbation method is used to study effective response of nonlinear Kerr composites, which are subject to the constitutive relation of electric displacement and electric field, Dα = εαE xα|E|2E. Under the external AC and DC electric field Eapp = Eα(1 sinwt), the effective nonlinear responses and local potentials are induced by the cubic nonlinearity of Kerr materials at all harmonics. As an example in three dimensions, we have investigated this kind of nonlinear composites with spherical inclusions embedded in a host. At all harmonic frequencies, the potentials in inclusion and host regions are derived. Furthermore, the formulae of the effective linear and nonlinear responses are given in the dilute limit.     

Effective Response of Nonlinear Composite under External AC and DC Electric Field

A perturbation method is used to study effective response of nonlinear Kerr composites, which are subject to the constitutive relation of electric displacement and electric field, Dα=εαE＋xα｜E｜^2E. Under the external AG and DC electric field Eapp = Eα（1 ＋ sinωt）, the effective nonlinear responses and local potentials are induced by the cubic nonlinearity of Kerr materials at all harmonics. As an example in three dimensions, we have investigated this kind of nonlinear composites with spherical inclusions embedded in a host. At all harmonic frequencies, the potentials in inclusion and host regions are derived. Furthermore, the formulae of the effective linear and nonlinear responses are given in the dilute Iimit.     

在自由空间里的运动磁场和时变磁场都没有产生电场

在自由空间里,磁场运动时没有产生电场、时变磁场的辐射运动也没有产生电场.故,“磁生电”的真实原因是：金属电子在广义洛伦兹磁力的作用下的流动而形成Ic,却不是法拉第-麦克斯韦-爱因斯坦在自由空间里虚构的位移电流Id.基于唯物主义自然观,联系电磁感应的物质是洛伦兹的金属电子,却不是法拉第-麦克斯韦-爱因斯坦的真空以太.     

高温超导体在对称和不对称外磁场中的悬浮力计算

在理想无限长直高温超导 -永磁导轨系统中 ,由于导轨磁场分布的不均匀性 ,超导体运动过程中所处外磁场有对称及不对称分布两种情况。原 Prigozhin模型假设超导体各向同性 ,但 YBCO高温超导体存在明显的各向异性。改进Prigozhin模型增加了原模型中的约束条件 ,考虑了这种各向异性。在对称外磁场中改进 Prigozhin模型的计算结果和原Prizhogin模型相同 ,因为原模型在对称外磁场中自然满足超导体各向异性。在不对称外磁场中计算结果和实验结果吻合较好 ,而原模型计算结果和实验结果差别较大。所以改进模型考虑了各向异性 ,适用于对称和不对称外磁场 ,能得到更准确的计算结果。     

Magnetic and Magneto-Optical Properties in Paramagnetic NdF3 Under High Magnetic Field

In this paper, we first theoretically report the magnetic and magneto-optical properties in paramagnetic media under high external magnetic field. Considering the action of the external magnetic field H_e and indirect exchange interaction H_v, the characteristic of the magnetic saturation and the property of the Faraday rotation to be nonlinear with external magnetic field are presented in paramagnetic NdF₃. In terms of our theory, the indirect exchange interaction plays an important role in the magnetization M and the Faraday rotation θ in NdF₃ under high external magnetic field. The theory is in good agreement with experimental results. On the other hand, a reasonable explanation for the temperature dependence of the ratio of the Verdet constant to the magnetic susceptibility V/χ is obtained.