Novel Studies of Vortex Matter and Peak Effect using In-Situ Neutron Scattering and AC Magnetization

这项个人研究者奖是颁给一位年轻的教授，表彰他利用原位中子散射和交流磁化测量，研究了ii型超导体中与峰值效应相关的涡旋物质相和相变。尽管ii型超导体在技术上具有重要意义，但人们对涡旋物质相的了解甚少。多年来，由于随机钉钉的破坏作用，人们认为涡旋物质系统中不可能发生真正的有序-无序（熔化）相变。最近有人提出，在弱无序的ii型超导体中可能存在拓扑有序的涡旋固相（布拉格玻璃）。布拉格玻璃相的熔融（无序）被认为是许多ii型超导体中所见的众所周知但知之甚少的峰值效应异常的起源。有初步的实验证据表明，峰值效应是超导涡旋物质中真正的有序-无序相变。该项目将使用原位小角中子散射来确定经典ii型超导体Nb中的涡旋物质相图。研究了无序对涡旋物质过冷和过热的影响。本项目还将探索中子自旋回波技术在亚稳态涡旋相研究中的可能应用。这些研究将建立对ii型超导体磁性的基本认识。参与该项目的研究生和本科生将有机会在NIST的高分辨率中子散射中心和法国格勒诺布尔的朗格万研究所与来自世界各地的研究人员一起工作。这应该为学生将来在学术界、工业界或政府的职业生涯做好准备。ii型超导体中的涡流形成了一个具有技术和科学兴趣的凝聚态物质系统。超导体在技术上引起了人们的兴趣，因为它们能够承载高电流而不会因电阻而损耗。超导体的载流能力是由涡旋-涡旋相互作用、随机钉住（涡旋-引脚相互作用）和热波动之间的微妙竞争决定的。尽管ii型超导体在技术上具有重要意义，但人们对涡旋物质相的了解甚少。这个个人研究者奖是给一位年轻的教授，他将使用原位中子散射和交流磁化测量来研究涡旋物质的物理学。这些研究将建立对ii型超导体磁性的基本认识。参与该项目的研究生和本科生将有机会在NIST的高分辨率中子散射中心和法国格勒诺布尔的朗格万研究所与来自世界各地的研究人员一起工作。这应该为学生将来在学术界、工业界或政府的职业生涯做好准备

This individual investigator award is to a young professor for a study of vortex matter phases and phase transitions related to the peak effect in type-II superconductors, using in situ neutron scattering and ac magnetization measurements. In spite of the technological importance of type-II superconductors, the vortex matter phases are poorly understood. For many years, it was thought that a genuine order-disorder (melting) phase transition cannot occur in vortex matter systems due to the destructive effects of random pinning. Recently it was proposed that a topologically ordered vortex solid phase (Bragg glass) could exist in weakly disordered type-II superconductors. The melting (disordering) of the Bragg glass phase has been suggested as the origin of the well known but poorly understood peak effect anomaly seen in many type-II superconductors. There is preliminary experimental evidence suggesting that the peak effect is a genuine order-disorder phase transition in the superconducting vortex matter. This project will use in situ small angle neutron scattering to determine the vortex matter phase diagram in a classic type-II superconductor, Nb. The effects of disorder on the supercooling and superheating of vortex matter will be investigated. This project will also explore a possible application of neutron spin echo technique for studying the metastable vortex phases. These studies will establish a basic understanding of the magnetic properties of type-II superconductors. The graduate and undergraduate students participating in this project will have the opportunity to work at the Center for High-Resolution Neutron Scattering at the NIST and at the Institut Laue Langevin in Grenoble, France with researchers from around the world. This should prepare the students for future careers in academia, industry, or government.%%%Vortices in type-II superconductors form a condensed matter system of technological and scientific interests. Superconductors are of technological interest because they are able to carry high electrical currents without loss due to resistance. The current-carrying capability of a superconductor is determined by a subtle competition between the vortex-vortex interactions, the random pinning (vortex-pin interactions), and thermal fluctuations. In spite of the technological importance of type-II superconductors, the vortex matter phases are poorly understood. This individual investigator award is to a young professor who will study the physics of vortex matter using in situ neutron scattering and ac magnetization measurements. These studies will establish a basic understanding of the magnetic properties of type-II superconductors. The graduate and undergraduate students participating in this project will have the opportunity to work at the Center for High-Resolution Neutron Scattering at the NIST and at the Institut Laue Langevin in Grenoble, France with researchers from around the world. This should prepare the students for future careers in academia, industry, or government.***