Experimental Investigations of the Thermodynamics and Pinning in the Charge-Density Wave System Potassium- Molybdate

钼酸钾电荷密度波系热力学和钉扎实验研究

• 批准号: 9103277
• 负责人: Stuart Brown
• 金额: --
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-06-01 至 1992-01-17
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9103277&HistoricalAwards=false
• 关键词: Experimental; Investigations; Thermodynamics; Pinning; Charge

This research is concerned with unresolved fundamental problems associated with the charge-density-wave (CDW) transition, namely the nature and effects of fluctuations in the neighborhood of the CDW transition and secondly the nature of the very weak impurity interactions with the CDW. The role of phonon entropy on the thermodynamics of the CDW transition will be studied. Improved specific heat, elastic, and magnetization measurements will permit a more careful confirmation of scaling laws. A novel resonant ultrasonic method will be used for simultaneous evaluation of all components of the elastic modulus tensor as a function of temperature. Presently, thermodynamic measurements do not yet confirm the criticality temperature range shown by x-ray diffraction. Susceptibility measurements will be attempted to further explore the validity of the scaling laws. It is hoped to provide experimental evidence on the influence of fluctuations on charge and heat transport and to compare these results with thermodynamic quantities. A second portion of the research is concerned with the synthesis of patassium molybdate with isotopic substitution on the oxygen (0) site with the obtainment of well controlled ratios of 180/160 or 170/160. Both transport and nuclear magnetic resonance measurements will be undertaken to obtain evidence on the pinning of the CDW. A search for the effects of the isotopic substitution on the CDW phase transition will be made. This will be the first attempt to explore isotopic effects on CDW systems.

这项研究涉及尚未解决的基本问题 与电荷密度波（CDW）跃迁相关，即 的性质和影响的波动在附近的 CDW跃迁和极弱杂质的性质 与CDW的互动。 声子熵在 将研究CDW转变的热力学。 改进 比热、弹性和磁化测量将允许 更仔细地证实了比例定律。 一种新型的谐振 超声方法将用于同时评价所有 作为函数的弹性模量张量的分量 温度 目前，热力学测量还没有 确认x射线显示的临界温度范围 衍射法 将尝试进行敏感性测量， 进一步探讨标度律的有效性。 是希望 提供实验证据，说明波动对 电荷和热传输，并将这些结果与 热力学量 研究的第二部分是 与同位素合成钾有关， 在氧（0）位点上取代， 控制比例为180/160或170/160。 运输和核 将进行磁共振测量以获得 关于CDW的证据。 对影响的研究 对CDW相变进行同位素替代。 这将是首次尝试探索同位素对CDW的影响 系统.