RUI: Core Size Effects on Flux-Flow Resistivity: Collaborative Project to Launch a Program Exploring Flux Dynamics in Weak-Pinning Systems

摘要，非技术性：该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)资助的。美国迫切需要对其老化的电网进行现代化改造，这一事实最近在2003年8月东北部大范围停电中得到了突显。此外，目前电网中使用的导电材料会向环境释放废热，每年价值数十亿美元的电力永远不会到达用户手中。这是由于传统导体的耗散电阻造成的。另一方面，超导体的导电率为零。因此，美国和世界各地的科学家和工程师正在积极开发用于电网现代化的超导线路，这使得对超导化合物的电磁性质的了解成为主要的研究重点。其中，一套关键的机制是在各种条件下磁场如何穿透技术相关超导体的内部。这种穿透是以漩涡的形式发生的吗？离散的磁通量量子，它们也相互作用。这些涡旋的运动极大地影响了超导体的载流能力，因此涡旋动力学的本质得到了广泛的研究。本项目的兴趣在于这些涡旋的内部结构或核心如何影响它们的自由运动？很少有人研究，因为自由运动是在技术上具有挑战性的条件下实现的，只有这一组人和其他几个人才能实现。该项目还旨在由本科生运营，从而为他们在科学领域的职业生涯做好准备。摘要：该奖项由2009年美国复苏和再投资法案(公法111-5)资助。磁通量量子(也称为涡旋、磁力线或磁通子)的动力学？外加磁场如何开始穿透技术上相关的第二类超导体的内部？在理解和应用这些材料，尤其是高温铜酸盐方面，仍然是研究的重点。不同的小组正在探索的一个特定方面是这些磁通量子的非超导核心的性质，这仍然不完全清楚，但已经知道影响磁通量子之间的相互作用，从而影响磁通物质中相变的性质。在各种情况下。本项目唯一准备探索的磁芯的一个很少研究的方面是磁芯的影响，特别是对磁流电阻率的场依赖性的影响，这是与自由磁流(FFF)相关联的直流驱动的耗散，FFF相是一种高度有序的动态相，在FFF相中，磁通物质的弹性克服了无序诱导的钉扎和热波动。与直流传输测量相补充的是同一样品的磁化强度、热容和核磁共振？通过现在和未来的合作。所有这些都将在至少四种不同材料的现有高质量晶体上进行，以探索依赖化合物的微妙之处。最终目标是提供一个独特的、全面的观点来了解磁通核心的性质。该项目还旨在为物理学本科生提供研究经验，为研究生学习及以后的学习做准备；因此，学生将积极参与。

Abstract, non-technical:This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The US is in dire need to modernize its aging electric power grid, a fact underscored recently by the widespread power outage in the Northeast in August 2003. Also, the conducting materials used in the present grid release waste heat to the environment, worth billions of dollars annually in electricity that never reaches its users. This is due to the dissipative resistance in conventional conductors. Superconductors, on the other hand, conduct electricity with zero dissipation. Thus, scientists and engineers throughout the US and around the world are actively developing superconducting lines for grid modernization, which has made the understanding of the electromagnetic properties of superconducting compounds a major research priority. Of these, one critical set of mechanisms is in how magnetic fields penetrate the interior of technologically relevant superconductors under various conditions. Such penetration occurs in the form of vortices ? discrete quanta of magnetic flux which also interact with each other. The motion of these vortices greatly affects the current-carrying capability of superconductors; thus the nature of vortex dynamics has been widely investigated. The interest in the present project is in how the internal structure or cores of these vortices affect their free motion ? something rarely studied, since free motion is achieved under technically challenging conditions achieved only by this group and few others. The project is also designed to be run by undergraduate students, thus preparing them for careers in science.Abstract, technical:This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The dynamics of magnetic flux quanta (also known as vortices, flux lines, or fluxons) ? by which an external magnetic field begins to penetrate the interior of technologically relevant type II superconductors ? continues to be a research priority in understanding and applying these materials, most notably high-temperature cuprates. A particular aspect being explored by various groups is the nature of the non-superconducting cores of these flux quanta, which is still not completely understood but is already known to affect the interactions between flux quanta and thus the nature of phase transitions in ?flux matter? under various conditions. One rarely studied aspect of flux cores which this project is uniquely poised to explore is the effect of cores particularly on the field dependence of flux flow resistivity, which is the DC-driven dissipation associated with the free flux flow (FFF) phase, a highly ordered dynamic phase wherein the elasticity of the flux matter overcomes disorder-inducing pinning and thermal fluctuations. Complementing the DC transport measurements are magnetization, heat capacity, and NMR on the same samples ? via present and future collaborations. All this is to be performed on already available, high-quality, crystals of at least four different materials to explore compound-dependent subtleties. The ultimate goal is to provide a uniquely comprehensive view into the nature of the flux core. The project is also designed to provide research experience to physics undergraduates in preparation for graduate studies and beyond; therefore students are to be actively involved.