Electrodynamics of Superconductors

小行星9623720 该项目旨在研究新型超导材料对微波频率电磁波的响应，如高温超导材料， 超导体和 碳化硼 超导体将使用某些独特的设施进行实验，以研究各种条件和材料下的微波响应。这 响应， 当适当地分析时，将产生关于这些材料中的电子配对状态和超导涡旋运动的重要信息。除了对高温和硼碳化物超导体的理解做出基础性贡献外，这项工作还将对 微波 应用. 了解纯系统的固有性质，纯度的影响，将提供线索，以提高微波器件的损耗能力。非线性效应的研究对提高微波器件的高功率性能至关重要，目前这严重限制了高温超导材料在这一竞技场的成功应用。 %%% 电磁 响应 的 高 和 低温超导体将利用独特的实验能力进行研究，涵盖广泛的频率（直流至50千兆赫）、温度（2至350开尔文）和磁场（0至7特斯拉）。 该计划将解决当前的关键问题，如序参数对称性，准粒子态密度，迈斯纳和混合态中磁场的破坏效应，c轴运输，包括相干/非相干准粒子隧穿和内在约瑟夫森结的可能性。高温超导体的一个显著特征是它们在中等微波功率和场振幅下的显著非线性响应。本计画的另一个主题是了解高频下磁通穿透的时空动态的非线性。 实验将进行非线性阻抗，混合acdc和谐波/互调响应，在频域和时域，并将在最近出现的临界状态模型的框架进行分析。 ***

9623720 Sridhar This project seeks to study the response to electromagnetic waves at microwave frequencies, of new superconducting materials, such as high temperature superconductors and borocarbide superconductors. Experiments will be carried out using certain unique facilities to study microwave response under a variety of conditions and materials. This response, when suitably analyzed, will yield important information about the paired state of electrons and the motion of superconducting vortices in these materials. In addition to making fundamental contributions to the understanding of high temperature and borocarbide superconductors, this work will also have important impact on microwave applications. An understanding of the intrinsic properties of the pure systems, the the influence of purities, will provide clues to improving the loss capabilities of microwave devices. The studies of non-linear effects will be crucial to improving the high power performance of microwave devices, currently a serious limitation to the successful application of the high temperature superconducting materials in this arena. %%% The electromagnetic response of high and low temperature superconductors will be investigated using a unique experimental capability, covering a wide range of frequencies (dc to fifty gigahertz), temperature (2 to 350 Kelvin) and magnetic field (0 to 7 Tesla). The program will address key current issues, such as order parameter symmetry, quasiparticle density of states, depairing effects of a magnetic field in the Meissner and mixed states, c-axis transport including coherent/incoherent quasiparticle tunneling and possibility of intrinsic Josephson junctions. A notable feature of the high temperature superconductors is their pronounced non-linear response at moderate microwave powers and field amplitudes. An understanding of this non-linearity in terms of th e spatio-temporal dynamics of flux penetration at high frequencies will be another theme of this project. Experiments will be carried out on the non-linear impedance, mixed acdc and harmonic/intermodulation response, in both the frequency-domain and time-domain, and will be analyzed in the framework of critical state models which can have recently emerged. ***