从FeSe_(0.5)Te_(0.5)的V～I曲线论磁通动力学的诸模型(英文)

高温超导体的发现动摇了支配磁通动力学二十几年的Kim-Anderson模型.于是人们提出了新的涡旋玻璃态模型,集体钉扎模型和U～j对数关系模型来描述高温超导体的磁通动力学.其中,涡旋玻璃态模型已被人们广泛接受.Fe基超导体发现后,人们它行为十分类似于高温超导体.我们实验上仔细研究了FeSe0.5Te0.5单晶的V～I关系曲线,发现上述诸模型均不能很好的解释我们的实验结果,而张的反跳模型恰能很好的拟合实验结果.本文讨论了诸模型对高温超导体磁通动力学描述的适用性并给出合理的解释.     

从FeSe0.5Te0.5的V～I曲线论磁通动力学的诸模型（英文）

高温超导体的发现动摇了支配磁通动力学二十几年的Kim-Anderson模型.于是人们提出了新的涡旋玻璃态模型,集体钉扎模型和U～j对数关系模型来描述高温超导体的磁通动力学.其中,涡旋玻璃态模型已被人们广泛接受.Fe基超导体发现后,人们它行为十分类似于高温超导体.我们实验上仔细研究了FeSe0.5Te0.5单晶的V～I关系曲线,发现上述诸模型均不能很好的解释我们的实验结果,而张的反跳模型恰能很好的拟合实验结果.本文讨论了诸模型对高温超导体磁通动力学描述的适用性并给出合理的解释.     

高温超导体电子态相图的新认识

简要介绍了高温超导体的电子态相图及最近的一些发展,通过测量高温超导体的抗磁信号,发现在过掺杂的高温超导体中存在着抗磁信号的第二个异常转变,分析发现这个转变可能对应着超导畴之间的耦合场,从而推论高温超导体在过掺杂区可能存在着电荷在介观尺度或宏观尺度上的不均匀,结合国际上非弹性中子散射的数据和超流电子密度的数据,文章作者第一次对电子态相图提出了一个自治的解释,这个结果如果得到其他方面的进一步验证,将对高温超导体机理的理解和更完善模型的建立起到重要指导作用。     

含有多种钉扎中心的层状高温超导体在其单个钉扎区域的钉扎机制

本文中，我们提出了一个关于含有多种钉扎中心的层状高温超导体在其单个钉扎中心的钉扎机制的理论，并讨论了具有两种钉扎中心的层状高温超导体的钉扎机制和临界电流密度．我们发现在强、弱钉扎中心之间存在着相互竞争，并解释了临界电流密度在低场区域随磁场增加而迅速降低的现象．     

弹道输运与高温超导电性

本文在引入了弹道输运的概念后,对高温超导体正常态下电阻率和霍耳效应的各向异性以及它们奇异的温度特性统一地进行了解释;对温差电势率的各向异性及其温度行为进行了讨论;也分析了高温超导体由正常态向超导态转变的过程,并给出了超导转变温度与材料一些物理参数的关系.     

高温超导体中的相分离

对高温超导体中的一种特殊现象———相分离作了简要介绍和讨论，希望有助于对高温超导体从其母体———反铁磁绝缘体到金属（超导态）的转变以及与此相关的高温超导体的物理性质的了解．文章分四部分：高温超导体的电子相图；高温超导体中相分离研究的内容及现状；有关相分离的物理机制；高温超导体中的条纹相．     

高温超导体的结构组装

 在总结铜氧化物高温超导体晶体结构特点的基础上，提出了以无限层结构Cu-O钙钛矿为核心的结构组装概念，通过和相关结构的外延组合，衍生出了高温超导体的主要晶体构型。进一步运用此观念，建立了新的三元数命名法，并对高温超导体的晶体结构进行了归类。     

非平衡态下高温超导体的光场致发射

外加电场的作用下高温超导体材料体内电子平衡态的化学势偏移导致出现非平衡状态，这种非平衡状态将影响高温超导体光场致发射的性质。本对高温超导体的光场致发射受非平衡态的影响进行了研究。     

氧化物高温超导体的双极化子解释的可能性

通过分析双极化子形成的条件,指出文献[1]给出的三元金属氧化物高温超导体的双极化子解释是可疑的。 关键词：     

高温超导体超导态的场致发射

高温超导体处在临界温度以下时，能隙会引起体内电子分布的改变。本文在考虑到能隙对体内电子分布影响时，分析了高温超导体的场致发射电流密度和场致发射电子能谱。     

铁基高温超导体电子结构的角分辨光电子能谱研究

铜氧化物超导体和铁基超导体是人类相继发现的两类高温超导家族,它们的高温超导机理是凝聚态物理领域中长期争论但悬而未决的重大问题.对铁基超导体广泛而深入的研究,以及与铜氧化物高温超导体的对比,对于发展新的量子固体理论、解决高温超导机理、探索新的超导体以及超导实际应用都具有重要意义.固体材料的宏观物性由其微观电子结构所决定,揭示高温超导材料的微观电子结构是理解高温超导电性的前提和基础.由于角分辨光电子能谱技术具有独特的同时对能量、动量甚至自旋的分辨能力,已成为探测材料微观电子结构的最直接、最有力的实验手段,在高温超导体的研究中发挥了重要作用.本文综述了在不同体系铁基超导体中费米面拓扑结构、超导能隙大小和对称性、轨道三维性和选择性、电子耦合模式等的揭示和发现,为甄别和提出铁基超导新理论、解决高温超导机理问题提供重要依据.     

高T_c超导体YBCO磁通钉扎的计算机模拟研究

临界电流密度Jc是影响高温超导体在强电领域应用的一个重要参数,在实际应用中,特别在外加磁场下,临界电流密度与超导材料的磁通钉扎性质密切相关.因此,磁通钉扎一直是高温超导体研究中的一个重要领域.由于高温超导体磁通钉扎力密度Fp的标度律存在,本文根据D.Dew-Hughes总结的钉扎力函数,主要存在两种主要作用类型(正常相和△K).我们将D.Dew-HugBes给出的钉扎力密度Fp标度函数改进为一个简化的具有物理意义的函数表达式.结合文献中已有的实验数据,我们对YBcO进行了计算机模拟,确定了它的磁通钉扎类型,模拟的研究结果与实际情况比较吻合.     

Dislocation structure and transport properties of low-angle tilt boundaries in high-temperature superconductors

A theoretical model that describes split grain-boundary dislocations in low-angle tilt boundaries of high-temperature superconductors is suggested. It is shown that the dissociation of dislocations in low-angle tilt boundaries is usually accompanied by a decrease in their elastic energy and causes an increase in the critical current density across the boundaries in high-temperature superconductors.     

Common phase diagram for low-dimensional superconductors

A phenomenological phase diagram which has been derived for high-temperature superconductors from NMR Knight-shift measurements of the pseudogap is compared to the phase diagram that is obtained for organic superconductors and spin-ladder superconductors, both low-dimensional systems. This is contrasted to the phase diagram of some Heavy Fermion superconductors, i.e. superconductors not constrained to a low dimensionality.     

第二代高温超导体研究与在聚变领域应用前景

简述了高温超导体的特点,系统介绍了第二代高温超导体的研究状况、制备工艺,并分析了第二代高温超导体在核聚变领域的应用前景。     

AC losses in high-temperature superconductors: revisiting the fundamentals of the loss modelling

The fundamentals of the electromagnetic modelling of high-temperature superconductors are discussed. Special attention is paid to intrinsic features of high-temperature superconductors different to those of low-temperature superconductors. Examples of those features are strong thermal fluctuations, which results in enhanced flux creep and slanted E(J)-characteristics, anisotropy of critical current density and material resistivity, and the granularity of the material. Having established the fundamental principles for the loss modelling, the influence of thermal fluctuations, anisotropy and granularity on the AC losses are considered.     

高压下富氢高温超导体的研究进展

近年来,高压强极端条件下的富氢化合物成为高温超导体研究的热点目标材料体系.该领域目前取得了两个标志性重要进展,先后发现了共价型H3S富氢超导体(Tc=200 K)和以LaH10(Tc=260 K,–13℃),YH6,YH9等为代表的一类氢笼合物结构的离子型富氢超导体,先后刷新了超导温度的新纪录.这些研究工作燃发了人们在高压下富氢化合物中发现室温超导体的希望.本文重点介绍高压下富氢高温超导体的相关研究进展,讨论富氢化合物产生高温超导电性的物理机理,展望未来在富氢化合物中发现室温超导体的可能性并提出多元富氢化合物候选体系.     

Physical processes in high-temperature superconductors at the interface between the vortex-filled and meissner regions

A technique has been proposed for investigating the magnetic microstate of high-temperature superconductors with a simultaneous analysis of the crystalline microstate of the sample with the aim of elucidating the specific features of the interaction between the crystalline and magnetic microstructures of polycrystalline high-temperature superconductors. Qualitatively new results have been obtained for samples with different microstructures. In particular, it has been found that the magnetic field dependences of the trapped magnetic flux density B _tr(H ₀) of polycrystalline and epitaxial films of high-temperature superconductors exhibit regular steps for both increasing and decreasing magnetic fields. The obtained results have demonstrated that, in strong magnetic fields, the studied epitaxial films, as well as bulk and thin-film polycrystalline high-temperature superconductors, “break down” into single domains, crystallites, and subcrystallites with different demagnetization factors. It has been revealed that the dependences B _tr(H ₀) also exhibit steps due to the simultaneous penetration of vortices into crystallites of approximately the same sizes and into more regularly arranged subcrystallites. As the quality of the samples increases, these steps become more pronounced because of the increase in the short-range order. The absence of steps in the dependence B _tr(H ₀) of the polycrystalline bulk samples clearly demonstrates the absence of long-range order in these samples. It is the vitreousness of the crystallographic microstructure of high-temperature superconductors which is responsible for the observed transformations in the vortex system. The similarity of the results obtained for samples with different microstructures indicates that the penetration (escape), distribution, and trapping of the magnetic flux in these samples occur through a universal mechanism. It has been found that the polycrystalline high-temperature superconductors are actually multi-step rather than two-step systems. It has been shown that the vitreousness of the microstructure of high-temperature superconductors and the presence of close-packed twin boundaries in samples lead to the penetration of a magnetic flux in the form of hypervortices into the sample and cause the formation of a superconducting glass state on a different physical basis as compared to the Ebner-Stroud model of a granulated glass.     

Effect of stress fields of small-angle tilt grain boundaries on structural inhomogeneities in high-temperature superconductors

The effect of dilatational stresses of grain boundaries on the atomic structure rearrangement near these boundaries in high-temperature superconductors is discussed. The concentration profiles characterizing the spatially inhomogeneous distribution of oxygen near small-angle tilt boundaries in Bi-Sr-Ca-Cu-O superconductors are calculated.     

Generalizing the Cooper-pair instability to doped Mott insulators

Copper oxides become superconductors rapidly upon doping with electron holes, suggesting a fundamental pairing instability. The Cooper mechanism explains normal superconductivity as an instability of a fermi-liquid state, but high-temperature superconductors derive from a Mott-insulator normal state, not a fermi liquid. We show that precocity to pair condensation with doping is a natural property of competing antiferromagnetism and d-wave superconductivity on a singly-occupied lattice, thus generalizing the Cooper instability to doped Mott insulators, with significant implications for the high-temperature superconducting mechanism.