Superconducting Pinning with Artificially Prepared Nanostructures

涡旋在自然界中普遍存在，从大气层、带电和不带电的等离子体、磁性和超导材料。在这个领域中的一个重要问题是如何锚这些旋涡，所谓的“钉扎”，因为物理性质的修改，在基本的方式，如果旋涡被钉扎。在超导体中出现了一种特别有趣的物理情况，即磁场通过形成超导涡旋阵列而穿透材料。这些旋涡可以钉扎人工制备的钉扎阵列，可以使用新的光刻技术生产。本计画致力于研究超导涡旋与奈米结构阵列相互作用所产生的基本问题。我们将研究诸如阵列几何形状、材料、钉扎位置形状的影响等问题。除了它的基本研究兴趣之外，这些研究可能导致减少自发噪声和增强材料的超导性能的方案。技术摘要超导体中的涡旋钉扎研究是一个有趣的基础研究领域，这对高临界电流带和低噪声超导器件的制造具有意义。人工制备的钉扎阵列与超导涡旋晶格之间的相互作用导致量子匹配现象，表现为在特定场下增强的临界电流和减小的电阻。 这个研究项目，将致力于（a）找到钉扎结构的类型，单独提供强大的钉扎涡，（B）引入适当的“缺陷”内的周期性阵列的引脚，如条纹和/或随机波动的钉扎网站的位置。(a)将增加周期性点钉的畴壁能量，并增加周期性条钉的磁场宽度，从而减少热波动，而（B）可以改变相称相的普适性类别，从而以基本方式抑制热波动。关于（a）的问题大多是材料特有的，涉及单个涡-销相互作用的微观机制。关于（B）的问题本质上是统计的，与涡格与针阵列的集体相互作用有关。这两个问题都将系统地进行研究，并通过广泛的实验合作和与活跃在该领域的理论团体的互动。

Non Technical AbstractVortices are prevalent in nature all the way from the atmosphere, charge and uncharged plasmas, magnetic and superconducting materials. An important issue in this field is the way to anchor these vortices, the so called "pinning" because physical properties are modified in fundamental ways if vortices are pinned. A particularly interesting physical situations arises in superconductors where the magnetic field penetrates the material by the formation of arrays of superconducting vortices. These vortices can be pinned by artificially prepared pinning arrays which can be produced using novel lithographic techniques. This project is dedicated to the study of fundamental issue which arise when superconducting vortices interact with nanostructured arrays. Issues such as the effect of the array geometry, materials, shape of the pinning sites will be studied.In addition to its basic research interest, these studies may lead to schemes for reducing spontaneous noise and enhancing the superconducting properties of the material.Technical AbstractThe study of vortex pinning in superconductors is an interesting basic research area, with implications for the fabrication of high critical current tapes and low noise superconducting devices. The interaction between artificially prepared pinning arrays and the superconducting vortex lattice leads to quantum matching phenomena which manifest as enhanced critical currents and decreased resistance at particular fields. This research project, will be dedicated to (a) finding the type of pinning structure which individually provides strong pinning of vortices, and (b) introducing appropriate "defects" within the periodic array of pins, such as stripes and/or random fluctuations on the pinning site positions. (a) will increase the domain wall energy for the periodic point pins and increase the magnetic field width for the periodic stripe pins, thereby reducing thermal fluctuations, while (b) can change the universality class of the commensurate phase, thereby suppressing thermal fluctuations in fundamental ways. The issues concerning (a) are mostly material-specific, involving the microscopic mechanism of individual vortex-pin interaction. The issues concerning (b) are statistical in nature, having to do with the collective interaction of the vortex lattice with the array of pins. Both of these issues will be investigate systematically, and through extensive experimental collaborations and interactions with theoretical groups active in the field.