NMR Investigations of the Static and Dynamic Properties of Spin Density Waves

小行星9319304 技术摘要：本计画的主要议题是各向异性导体中自旋密度波的静态与动态性质。核磁共振（NMR）自旋回波将被用作显微镜探针，与电输运结合。大部分工作将在Bechgaard盐（TMTSF）2X（X=PF6，ClO4，AsF6等）。“普通”和场诱导自旋密度波与不同程度的钉扎将进行调查。从这项工作中获得的物理量包括序参量的温度依赖性，凝聚体响应于阈值以下电场的位移，阈值以上的滑动速度，阈值以上滑动速度的时空分布，SDW记忆和repinning效应，以及 温度和频率依赖性 的 SDW 相位子波动 非技术摘要：这个项目的目的是研究几种导电有机材料的一种不寻常的性质。在低温下，导电电子形成半导体状态，具有称为自旋密度波（SDW）的起伏磁性结构。该SDW通常固定在底层材料缺陷上。然而，当一个高于一定阈值的小电场施加到材料上时，SDW就会滑动。在这些条件下，它成为一种新型的电流。要进行的测量是电导和核磁共振自旋回波研究这些SDW的基本属性。它们包括起伏磁场的大小，其大小如何随温度变化，其热振动，在电场驱动下如何移动，以及当电场被移除时它再次被钉扎的复杂方式。 p:\wickman\abstract\clark.doc

9319304 Clark Technical abstract: The main issues addressed by this project are the static and dynamic properties of spin density waves (SDW) in anisotropic conductors. Nuclear magnetic resonance (NMR) spin echoes will be used as a microscopic probe, in conjunction with electrical transport. Most of the work will be on the Bechgaard salts (TMTSF)2X (X=PF6, ClO4, AsF6, etc.). Both "ordinary" and field induced spin density waves with varying degrees of pinning will be investigated. The physical quantities to be obtained from this work include the temperature dependence of the order parameter, the displacement of the condensate in response to an electrical field below threshold, its sliding velocity above threshold, the spatial and temporal distribution of the sliding velocity above threshold, SDW memory and repinning effects, and the temperature and frequency dependence of SDW phason fluctuations. Non-technical abstract: The purpose of this project is to investigate an unusual property of several organic materials that conduct electricity. At low temperatures the conducting electrons form a semiconducting state with an undulating magnetic structure called a spin density wave (SDW). This SDW is usually pinned to the underlying material imperfections. When, however, a small electric field above a certain threshold is applied to the material, the SDW slides. Under these conditions, it becomes a new type of electrical current. The measurements to be made are electrical conduction and nuclear magnetic resonance spin echo studies of the basic properties of these SDWs. They include the size of the undulating magnetic field, how its size varies with temperature, its thermal vibrations, how it moves when driven by an electric field, and the complex way it becomes pinned again when the electric field is removed. p:\wickman\abstract\clark.doc