• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Scanning tunneling microscope studies of the high temperature superconductor BSCCO.
【24h】

Scanning tunneling microscope studies of the high temperature superconductor BSCCO.

机译：高温超导体BSCCO的扫描隧道显微镜研究。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

This dissertation covers measurements on the high temperature superconductor Bi2Sr2CaCu2O8+delta as performed with a low temperature, ultra high vacuum scanning tunneling microscope (STM). The work involves studying the issue of electronic inhomogeneity on nanometer length scales. The first section contains a brief introduction to BSCCO and some of its properties relevant to STM measurements. Then I discuss the STM itself in terms of principle of operation, construction, and associated measurement electronics.;The next section is of measurements on the nearly 4-lattice-constant periodic modulations in the density of states. These modulations exist in BSCCO both in the form of a charge-ordered state, which may represent new phases, and also as quasi-particle scattering, a band structure effect. To tell these two effects apart, I look at their dispersion (energy vs. wavelength) characteristics, and also the effect they have on the coherence peak heights. I show that the non-dispersive charge ordered state tends to exist most strongly in regions of large gap, which resembles the results of other studies of BSCCO at low dopings. Further analysis suggests that these modulations are fluctuating and have a uni-directional nature.;Finally I will focus on the (non-periodic) nano-scale electronic inhomogeneities seen in this material, namely the spatial variations of the superconducting gap. While it is known that BSCCO has regions of gaps that are smaller or larger than the average, the reason for the excessive heights of the coherence peaks in the small gap regions, or the short peaks in the large gap regions were unknown. I compare experimental data (taken with high spatial and energy resolution) to a numerical model that places a patch of one gap in a sea of another. The results show good qualitative agreement, both in the shapes of the coherence peaks and the spatial evolution of spectra from inside the region to outside. This is followed by analysis involving the energy moments to determine the true gap values.;In the appendix I include my work measuring the charge density wave (CDW) in the quasi-2D material TbTe3. The analysis indicates that the CDW is fully incommensurate with wave-vector qCDW ≈0.71 x 2pi/c. Imaging at various tip-sample voltages highlights effects of the sub-surface layer and its effect on the CDW. An additional (possibly surface) dimerization and ≈ 0.68 x 2pi/alpha ordering perpendicular to the CDW was also observed for the first time.
机译：本论文涵盖了在低温超高真空扫描隧道显微镜（STM）上对高温超导体Bi2Sr2CaCu2O8 +δ的测量。这项工作涉及研究纳米长度尺度上的电子不均匀性问题。第一部分简要介绍了BSCCO及其与STM测量相关的一些特性。然后，我将根据操作，构造和相关的测量电子学原理来讨论STM本身。下一部分是状态密度中近4晶格常数周期调制的测量。这些调制以电荷有序状态的形式存在于BSCCO中，可以表示新的相位，也可以作为准粒子散射的形式存在于带结构效应中。为了区分这两种效应，我研究了它们的色散（能量与波长）特性，以及它们对相干峰高的影响。我表明，在大间隙区域中，非分散电荷有序状态倾向于最强烈地存在，这与低掺杂下BSCCO的其他研究结果相似。进一步的分析表明，这些调制是波动的，并且具有单向性。最后，我将重点介绍这种材料中所见的（非周期性）纳米级电子不均匀性，即超导间隙的空间变化。虽然已知BSCCO的间隙区域小于或大于平均值，但未知的是小间隙区域中相干峰高度过大或大间隙区域中的短峰高度过高的原因。我将实验数据（以高空间分辨率和能量分辨率拍摄）与一个数值模型进行比较，该数值模型将一个缝隙的补丁放置在另一个缝隙的海洋中。结果表明，在相干峰的形状和光谱从区域内部到外部的空间演化方面，都具有良好的定性一致性。接下来是涉及能量矩的分析以确定真实的间隙值。在附录中，我包括我的工作，用于测量准2D材料TbTe3中的电荷密度波（CDW）。分析表明，CDW与波矢qCDW完全不相称＆ap; 0.71 x 2pi / c。在各种尖端样品电压下成像可突出显示表面下层的影响及其对CDW的影响。附加的（可能是表面的）二聚化和＆ap;第一次也观察到垂直于CDW的0.68 x 2pi / alpha顺序。

著录项

  • 作者

    Fang, Alan.;

  • 作者单位

    Stanford University.;

  • 授予单位 Stanford University.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 129 p.
  • 总页数 129
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 O49;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号