Electronic Properties, Magnetotransport and STM in Quasi-One-and-Two-Dimensional Metals

这项研究涉及电子结构的研究，由于 在较低的温度下， 三维金属、半金属和半导体。 研究 利用扫描隧道显微镜（STM）和原子力 原子力显微镜（AFM）检测原子和电子结构 与单个原子的尺度上的分辨率和相关的 结果与研究的影响，高磁场对 某些材料的电子输运性质。 的 待研究的材料包括过渡金属 硫族化物，以及更复杂的晶体，如钽 硒化镍 上述技术的这种组合提供了 电子修饰的独特特征 与CDW、SDW和混合密度波相关。 他们还 提供对CDW中的修饰的极其灵敏的检测 杂质掺杂引起的结构。 掺杂 trichalcogenides产生新的电子相，金属绝缘体 转换和修改的CDW，所有这些都可以通过STM检测到 光谱、AFM扫描和高磁场传输。 结果应提供对电子 由于密度的存在而改变的材料的性质- 电子气中的波以及电子 密度波由于杂质掺杂。 %%% 本研究中研究的高度各向异性金属， 与密度波相关的不寻常的电子特性 提供对材料的新电子改性的洞察。 通过扫描在原子尺度上研究这些性质 隧道显微镜（STM）和原子力显微镜（AFM）， 结合相关电子的宏观测量， 在高磁场传导现象，导致一个独特的 了解整个电子结构。 STM和AFM 研究提供了晶体结构和 原子水平上的电子结构。 这些方法 对杂质和缺陷的改变极其敏感， 可用于系统地跟踪杂质原子位置， 有序化和新电子相的形成 晶体 对电子和 磁输运性质将关联原子的变化， 配置和局部电子结构与整体 材料的电子响应。 发展这些 方法对于设计和测试 新型电子材料。

This research involves the study of electronic structure due to charge-density waves (CDWs) and spin-density waves (SDWs) in lower dimensional metals, semimetals and semiconductors. The research utilizes scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to detect both the atomic and electronic structure with resolution on the scale of individual atoms and correlates the results with studies of the effects of high magnetic fields on the electronic transport properties of the some materials. The materials to be investigated include transition metal chalcogenides, as well as more complex crystals such as tantalum nickel selenide. This combination of the above techniques provides a unique characterization of the electronic modifications associated with CDWs, SDWs and mixed density waves. They also provide extremely sensitive detection of modifications in the CDW structure as induced by impurity doping. Doping of trichalcogenides produces new electronic phases, metal-insulator transitions and modified CDWs, all of which can be detected by STM spectroscopy, AFM scanning and high magnetic field transport. Results should provide a detailed understanding of the electronic properties of materials as modified by the presence of density- waves in the electron gas as well as changes in the electronic density waves due to impurity doping. %%% The highly anisotropic metals being studied in this research and the unusual electronic properties associated with density-waves provide insight into new electronic modifications of materials. Studies of these properties on an atomic scale by scanning tunneling microscopy (STM) and atomic force microscopy (AFM), combined with macroscopic measurements of the associated electronic conduction phenomena in high magnetic fields, lead to a unique understanding of the overall electronic structure. The STM and AFM studies provide a picture of both the crystal structure and the electronic structure at the atomic level. These methods are extremely sensitive to modifications by impurities and defects and can be used to systematically follow impurity atom locations, ordering and the formation of new electronic phases in the crystals. The accompanying modifications of the electronic and magnetotransport properties will correlate the changes in atomic configuration and local electronic structure with the overall electronic response of the material. The development of these methods should be extremely useful for the design and testing of new electronic materials.