Dynamic Transitions in Magnetic Vortex Lattices

该个人研究者奖将资助一个项目，该项目将采用一种新的钉紧力显微镜与快速传输测量相结合，以解决涡旋动力学的关键问题。这包括：a)电流驱动亚稳态向稳定过渡的机制；B)运动涡相的性质和它们之间的过渡；C)边界对峰效应区动力学和相偏析的影响；D)涡旋状态下频率记忆的机制。计划中的钉钉力显微镜将成像的不是漩涡本身，而是不同钉钉力区域之间的对比。它将能够区分强钉住的无序涡旋状态和弱钉住的有序涡旋状态，其空间分辨率约为1微米，并且其工作将不限于低场。利用旋涡运动可以被冻结在原地和成像是非侵入性的事实，显微镜将能够以优异的时间分辨率（约1ms）分辨旋涡运动。这种方法将允许访问涡旋动力学制度不可能通过现有的涡旋成像技术。参与这项工作的学生和年轻研究人员将获得将新开发的新技术应用于感兴趣的问题的技能。他们将学到的知识和技能将对他们未来的研究和发展事业有用。在技术上使用ii型超导体的一个限制因素是，在特定的磁场强度下，会形成磁涡流。这些涡流会“去钉”，导致超导体失去零电阻状态。由于ii型超导体的大多数性质都受涡旋的物理特性支配，因此研究涡旋运动的物理特性具有重要的基础和技术意义。几个新发现的现象清楚地表明，我们目前对涡旋动力学（或运动）的理解是有缺陷的。看来，由于随机钉住力的存在，相变和涡旋运动的开始是非常有趣的，比原来想象的更复杂。这个个人研究者奖将资助一个项目来解决这些问题，通过在涡旋阶段用一种新型的高分辨率显微镜来成像钉住力的分布，我们计划在我们的实验室里建造。一个强大的教育成分将是该项目的一个组成部分。研究生和本科生以及博士后都将积极参与该计划的所有研究和开发方面。他们将学到的知识和技能将对他们未来的研究和发展事业有用

This individual investigator award will fund a project that will employ a new pinning-force microscope in conjunction with fast transport measurements, to address key questions on vortex dynamics. These include: a) the mechanism of current driven metastable to stable transitions; b) the nature of moving vortex phases and the transitions between them; c) effects of boundaries on dynamics and phase segregation in the peak effect region; d) the mechanism of frequency memory in vortex states. The planned pinning force microscope will image not the vortices themselves but the contrast between regions with different pinning forces. It will be capable of distinguishing between a strongly pinned disordered vortex state and a weakly pinned ordered one with spatial resolution of about 1micro-m, and its operation will not be limited to low fields. By taking advantage of the fact that the vortex motion can be frozen in place and that the imaging is non-invasive, the microscope will be capable of resolving vortex motion with excellent temporal resolution (about 1ms). This method will allow access to regimes of vortex dynamics not possible by existing vortex imaging techniques. The students and young researchers involved in this work will gain skill in applying newly developed new techniques to questions of interest. The knowledge and skills that they will learn will be of use to them in future research and development careers.%%%A limiting factor to the use of Type-II superconductors in technology is that at a particular magnetic field strength, magnetic vortices form. These vortices can become "de-pinned" which then cause the superconductor to loose its zero resistance state. Because most properties of Type-II superconductors are governed by the physics of vortices, it is of fundamental and technological interest to study the physics of the motion these vortices. Several newly discovered phenomena have made it clear that our present understanding of vortex dynamics (or motion) is flawed. It appears that, due to the presence of a random pinning force, the phase transitions and the onset of vortex motion are very interesting and more complex than originally thought. This individual investigator award will fund a program to address these issues by imaging the pinning force distribution in the vortex phases with a novel high resolution microscope that we propose to build in our laboratory. A strong educational component will be an integral part of the project. Students at both graduate and undergraduate levels as well as a post doctoral fellow will actively participate in all research and development aspects of the program. The knowledge and skills that they will learn will be of use to them in future research and development careers.***