NMR Investigations of Spin Density Waves in Organic Metals and Vortices in Superconductors

本实验研究项目采用核磁共振技术研究了CDW和SDW一维系统中局部破缺对称基态结构的热运动和驱动运动，以及几种ii型超导体中涡旋结构的运动。研究的有机金属体系包括贝加德盐合金体系和蓝青铜。大多数实验将在非常宽的频率范围和高压下使用脉冲核磁共振。在超导体中，最近的核磁共振自旋回波场摇测量将扩展到各向异性超导体，以测量穿透深度的各向异性；并到高场测量相干长度。计划开展工作，以扩展最近在各向异性II型超导体中利用核磁共振对射频辅助磁通晶格退火的观察结果。一些非常高磁场的工作将在国家高磁场实验室进行。这项对新材料中不寻常基态的研究将扩展知识库，并有可能在基础固态物理学中产生重大进展。它还将演示使用核磁共振的新方法，这可能适用于其他情况。本实验研究项目主要使用核磁共振（NMR）技术来探测新型有机金属导体的基本电学特性，以及高各向异性超导体的磁性行为方面。感兴趣的有机导体表现出接近一维的导电。它们的导电被认为是通过一种被称为“滑动电荷密度波”的新机制发生的，与传统金属不同，它涉及载流子的高度相关运动。这种不同寻常的效应的特性，以及能够表现出这种效应的材料，都引起了人们的兴趣。这项研究的结果可能包括不寻常的新效果或材料，可能会在技术上找到新的应用。部分工作将在国家强磁场实验室进行。这个研究项目是跨学科的，涉及研究生和研究生，他们将接受良好的培训，进入工业、政府或教育部门的职位。＊＊＊

w:\awards\awards96\num.doc 9705369 Clark This experimental research project employs techniques of nuclear magnetic resonance in study of the thermal and driven motions of the local broken symmetry ground state structures in CDW and SDW one-dimensional systems, and the motion of vortex structure in several Type-II superconductors. Organic metal systems for study include a Bechgaard salt alloy system and the blue bronze. Most of the experiments will employ pulsed NMR over a very wide range of frequencies and up to high pressures. In superconductors, recent NMR spin-echo field-rocking measurements will be extended to anisotropic superconductors to measure the anisotropy of the penetration depth; and to high field to measure the coherence length. Work is planned to extend the recent observations by NMR of rf-assisted flux-lattice annealing in anisotropic Type- II superconductors. Some very high magnetic field work will be performed at the National High Magnetic Field Laboratory. This study of unusual ground states in novel materials will extend the knowledge base and has potential to generate significant advances in basic solid state physics. It also will demonstrate new methods for using NMR which may be applicable in other circumstances. %%% This experimental research project uses primarily the technique of Nuclear Magnetic Resonance (NMR) to probe basic electrical properties of novel organic metal conductors, as well as aspects of the magnetic behavior in highly anisotropic superconductors. The organic conductors of interest exhibit nearly one-dimensional electrical conduction. Their electrical conduction is believed to occur by a novel mechanism known as a "sliding charge density wave", which involves a highly correlated motion of carriers, unlike conventional metals. The properties of this unusual effect, and materials that can exhibit it, a re of interest. Results from this research may include unusual new effects or materials which may find new application in technology. A portion of the work will be carried out at the National High Magnetic Field Laboratory. This research project is interdisciplinary in nature and involves both graduate and postgraduate students who will be excellently trained to enter positions in industry, government or education. ***