Electro-Optic Studies of Charge Density Wave Conductors

电荷密度波导体的电光研究

• 批准号: 0400938
• 负责人: Joseph Brill
• 金额: --
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0400938&HistoricalAwards=false
• 关键词: Electro; Optic; Studies; Charge; Density

Charge-density-wave (CDW) materials in which the CDW can be depinned with a small electric field serve as model systems studies of the interactions of a periodic medium with quenched disorder. This single-investigator award supports the continued investigation of an unusual electro-optic effect, associated with CDW polarization in an applied field. The effect was discovered by the P.I.'s group several years ago. This effect is unlike conventional electro-optic effects. It occurs over a wide spectral range (at infrared energies below the CDW gap), occurs at very low electric fields (less than 0.1 V/cm, corresponding to the fields needed to depin the CDW), and varies spatially within the sample, changing sign in the sample's center. The emphasis of this project will be to more fully characterize the effect with the aim of obtaining a better understanding of its underlying physics. In the process an increased understanding of CDW interactions with phonons and uncondensed electrons, and the dynamics of CDW polarization will be obtained. Materials to be studied are the quasi-one dimensional CDW conductors tantalum trisulfide, niobium triselenide, and potassium molybdate ("blue bronze"). Electro-reflectance and electro-transmittance experiments at the University of Kentucky, carried out with tunable diode lasers, will be complemented with measurements at the Advanced Light Source, providing a broad educational experience for the students working on the project.Materials whose optical properties are modified by application of a voltage are known as electro-optic materials. They are the basis of optical communications and therefore are of increasing technological importance. Recently, the P.I.'s group at the University of Kentucky discovered that "charge-density-wave" (CDW) conductors, materials in which the electron density oscillates with a typical wavelength of one nanometer (one billionth of a meter), exhibit a number of very unusual electro-optic properties. In particular, voltage dependent changes in the transmittance and reflectance of electro-magnetic waves occur over a very wide infrared spectral range. These changes occur at very small voltages (e.g. 0.01 V across a 1 mm long sample), and vary with position within the sample.. This award supports a project to continue characterization of the effect in a few CDW materials, with the goal of better understanding its underlying physics and the properties of CDW's in general. Experiments will be carried out using tunable infrared diode lasers, representing one of the few applications of these devices for solid state spectroscopy. These studies will be complemented with experiments at the Advanced Light Source at Lawrence Berkeley National Laboratory, providing a broad instructional experience for the students working on the project.

电荷密度波（CDW）材料可以用一个小的电场来确定电荷密度波，它可以作为具有淬灭无序的周期性介质相互作用的模型系统研究。这个单一研究者奖支持在应用领域中继续研究与CDW偏振相关的不寻常的电光效应。这种效应是由私家侦探发现的几年前，他加入了他的团队。这种效应不同于传统的电光效应。它发生在很宽的光谱范围内（在CDW间隙以下的红外能量处），发生在很低的电场下（小于0.1 V/cm，对应于CDW脱落所需的电场），并且在样品内部发生空间变化，在样品中心改变符号。这个项目的重点将是更全面地描述这种效应，以便更好地理解其潜在的物理特性。在此过程中，我们将进一步了解CDW与声子和非凝聚电子的相互作用，以及CDW极化的动力学。拟研究的材料是准一维CDW导体三硫化钽、三硒化铌和钼酸钾（“蓝青铜”）。肯塔基大学用可调谐二极管激光器进行的电反射和电透射实验，将与先进光源的测量相辅相成，为从事该项目的学生提供广泛的教育经验。其光学性质因施加电压而改变的材料称为电光材料。它们是光通信的基础，因此在技术上越来越重要。最近，私家侦探肯塔基大学的研究小组发现，“电荷密度波”（CDW）导体，即电子密度以一纳米（一米的十亿分之一）的典型波长振荡的材料，表现出许多非常不寻常的电光特性。特别是，电磁波的透射率和反射率的电压依赖性变化发生在非常宽的红外光谱范围内。这些变化发生在非常小的电压下（例如0.01 V穿过1毫米长的样品），并随样品内的位置而变化。该奖项支持一个项目，继续表征一些CDW材料的效应，目的是更好地了解其基本物理和CDW的一般特性。实验将使用可调谐红外二极管激光器进行，这是这些设备在固态光谱中的少数应用之一。这些研究将与劳伦斯伯克利国家实验室的先进光源实验相辅相成，为从事该项目的学生提供广泛的教学经验。