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The development and implementation of electromechanical devices to study the physical properties of Sr2IrO4 and TaS 3.

机译：研究Sr2IrO4和TaS 3物理性质的机电设备的开发和实施。

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摘要

Transition metal oxides (TMO) have proven to exhibit novel properties such as high temperature superconductivity, magnetic ordering, charge and spin density waves, metal to insulator transitions and colossal magnetoresistance. Among these are a spin-orbit coupling (SOC) induced Mott insulator Sr2IrO4. The electric transport properties of this material remain finite even at cryogenic temperatures enabling its complex electronic structure to be investigated by a scanning tunneling microscope. At T = 77 K, we observed two features which represent the Mott gap with a value of 2Delta ∼ 615 meV. Additionally an inelastic loss feature was observed inside this gap due to a single magnon excitation at an energy of ∼ 125 meV. These features are consistent with similar measurements with other probes. In addition to these features, at T = 4.2 K lower energy features appear which are believed to be due to additional magnetic ordering. Another material that exhibits a unique physical behavior is the sliding charge density wave (CDW) material TaS3. It is a quasi-one dimensional material that forms long narrow ribbon shaped crystals. It exhibits anomalies including non-ohmic conductivity, a decrease in the Young's modulus, a decrease in the shear modulus and voltage induced changes in the crystal's overall length. In addition, we have observed the torsional piezo-like response, voltage induced torsional strain (VITS), in TaS3 which was first discovered by Pokrovskii et al. in 2007. Our measurements were conducted with a helical resonator. The VITS response has a huge effective piezoelectric coefficient of ∼ 10--4 cm/V. In addition we have concluded that the VITS is a very slow response with time constants of ∼ 1 s near the CDW depinning threshold, that these time constants are dependent on the CDW current, and we suggest that the VITS is due to residual twists being initially present in the crystal.;KEYWORDS: scanning tunneling microscope, Mott insulator, spin-orbit coupling, charge density wave, voltage induced torsional strain.
机译：过渡金属氧化物（TMO）已证明具有新颖的特性，例如高温超导性，磁有序性，电荷和自旋密度波，金属到绝缘体的过渡以及巨大的磁阻。其中有自旋轨道耦合（SOC）感应的Mott绝缘子Sr2IrO4。即使在低温下，该材料的电输运性能也仍然有限，从而可以通过扫描隧道显微镜研究其复杂的电子结构。在T = 77 K时，我们观察到两个特征，它们代表了Mott间隙，其值为2Delta〜615 meV。另外，由于在〜125 meV的能量下的单个磁振子激发，在该间隙内观察到了非弹性损耗特征。这些功能与其他探头的类似测量结果一致。除这些特征外，在T = 4.2 K时，还出现了较低的能量特征，这被认为是由于附加的磁排序。表现出独特物理行为的另一种材料是滑动电荷密度波（CDW）材料TaS3。它是准一维材料，可形成细长的带状晶体。它表现出异常，包括非欧姆电导率，杨氏模量降低，剪切模量降低以及电压引起的晶体总长度变化。此外，我们已经在TaS3中观察到了扭转压电式响应，即电压引起的扭转应变（VITS），这是由Pokrovskii等人首次发现的。在2007年。我们的测量是使用螺旋共振器进行的。 VITS响应具有约10--4 cm / V的巨大有效压电系数。此外，我们得出的结论是，VITS是一个非常缓慢的响应，其时间常数接近CDW固定阈值，约为1 s，这些时间常数取决于CDW电流，因此我们建议VITS是由于残余扭曲最初引起的关键词：扫描隧道显微镜，莫特绝缘子，自旋轨道耦合，电荷密度波，电压引起的扭转应变。

著录项

  • 作者

    Nichols, John.;

  • 作者单位

    University of Kentucky.;

  • 授予单位 University of Kentucky.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 163 p.
  • 总页数 163
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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