Phase Slip, Relaxation, and Field Effects in Charge-Density-Wave Conductors

电荷密度波导体中的相滑移、弛豫和场效应

• 批准号: 9424572
• 负责人: Robert Thorne
• 金额: $ 22.5万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-01 至 1998-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9424572&HistoricalAwards=false
• 关键词: Phase; Slip; Relaxation; Field; Effects

9424572 Thorne Charge-density-wave (CDW) phase slip and CDW relaxation as well as a recently discovered CDW field-effect modulation of CDW conduction will be explored. Transport and x-ray scattering experiments have indicated that phase slip is driven by strains in the CDW, that it occurs via homogeneous thermal nucleation of dislocation loops, and that slips strongly modify the strain profile near current contacts. The spatial distribution of phase slip and strain between and beyond current contacts will be measured, and compared with models for CDW dislocation nucleation and motion. Spatially-resolved measurements of noise and Shapiro steps will determine the effect of phase slips on CDW dynamics. The coherence of the CDW response will be probed near the Peirels transition, where phase slips should become very easy and the effect of impurity strains on slip may become important. Measurements in semiconducting materials such as TaS3 will investigate the effect of quasiparticle density on phase slip, which may be dramatic at low densities and low temperatures. Detailed spatially resolved measurements of time dependent CDW relaxation will be performed, in an attempt to develop quantitative understanding of the underlying mechanisms. Experiments will be performed to investigate the modulation of CDW conductance using FET-like structure were the semiconductor is replaced by a CDW conductor. %%% Charge density wave (CDW) conductors are among the richest systems in condense matter physics, and serve as a paradigm for study of many fundamental issues occurring in a variety of systems such as superconductors, insulators, materials growth ...etc. CDWs can be represented as a sinusoidal modulation of the electronic charge density occurring in materials with specific properties. The electrons in a CDW respond collectively and with some degree of coherence to ex ternal excitations such as electric fields. This proposal investigates the phase slip process, which is the process by which the CDW electrons are converted into normal electrons, near the contacts, in order to carry electricity from the CDW sample into the remaining part of the circuit. A number of electrical transport experiments are designed to explore the phase slip mechanism and related relaxation mechanisms as well as a recently discovered field- effect modulation of the CDW conduction. ***

小行星9424572 电荷密度波（CDW）相位滑移和CDW弛豫以及最近发现的CDW场效应调制CDW传导将被探讨。运输和X-射线散射实验表明，相滑移是由CDW中的应变驱动的，它通过位错环的均匀热成核而发生，并且滑移强烈地修改电流接触附近的应变分布。将测量电流接触之间和之外的相滑移和应变的空间分布，并与CDW位错成核和运动的模型进行比较。空间分辨的噪声和夏皮罗步骤的测量将确定CDW动力学上的相位滑移的效果。 CDW响应的相干性将在Peirels转变附近被探测，在那里相位滑移应该变得非常容易，并且其影响将被忽略。 杂质应变对滑移的影响可能变得重要。 在半导体材料如TaS 3中的测量将研究准粒子密度对相滑移的影响，这在低密度和低温下可能是戏剧性的。 CDW弛豫随时间变化的详细空间分辨测量 将进行一次尝试 到 发展定量 理解 的 底层 机制等 实验将进行调查的调制CDW电导使用FET类结构的半导体被取代的CDW导体。 电荷密度波（CDW）导体是凝聚态物理学中最丰富的系统之一，并作为研究各种系统中发生的许多基本问题的范例，如超导体，绝缘体，材料生长... CDW可以表示为在具有特定性质的材料中发生的电子电荷密度的正弦调制。CDW中的电子集体地并且以某种程度的相干性对外部激发（例如电场）作出响应。该提议研究了相位滑移过程，该过程是CDW电子转换为正常电子的过程 电子，靠近触点， 到 将电流从CDW样本传输到电路的其余部分。 大量的电输运实验 旨在探索相位滑移机制， 相关的弛豫机制，以及最近发现的场效应调制的CDW传导。 ***