Microwave Studies of the Metal-Insulator Transition with a Helical Resonator

用螺旋谐振器进行金属-绝缘体转变的微波研究

• 批准号: 9803969
• 负责人: Theodore Castner
• 金额: --
• 依托单位: University of Massachusetts Lowell Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-01 至 2001-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9803969&HistoricalAwards=false
• 关键词: Microwave; Studies; Metal; Insulator; Transition

3 9803969 Castner This is a condensed matter physics project that will investigate frequency dependent transport properties of the heavily doped semiconductors Si:P, Si:As, and other systems, close to the metal- insulator transition (MIT) using a helical resonator. The helical resonator allows measurements in the frequency range 100 MHz to 3 GHz. Measurements of both sample-induced frequency shifts and quality factor changes will yield information about the dielectric response and conductivity of semiconductor samples as a function of dopant levels near the MIT. The primary objectives of the project are (1) to clarify the nature of localization and interaction corrections the complex dielectric response of barely metallic samples in order to compare with theory, (2) to search for an unusual frequency dependence of conductivity at the critical concentration, as temperature is lowered, and (3) to extend the microwave measurements to frequencies well above 3 GHz using conventional network analyzers and resonant microwave cavities. Addition research will involve a study of the electron spin resonance (ESR) linewidths of antimony doped Si. All of these measurements bear on the general problem of conductivity in highly correlated electron systems. The results will be relevant to a number of related scientific areas including the high-Tc superconductivity problem. The project exposes graduate students to fundamental physics and provides experience with a number of electrical measurement techniques. Students associated with the project are prepared for a range of career opportunities. %%% Silicon, as the most important electronic material today, has been extensively studied for more than four decades. Heavily doped silicon exhibits an insulator-to-metal transition as the doping of donors or acceptors is increased above a critical density. Although static transport and thermal properties of this phase transition have been extensively studied there is still no generally accepted understanding of this unusual phase transition which features disorder, electron-electron interactions, and strong electron correlation. Although some infrared data exists there has been insufficient study of the dynamical properties of metallic samples as a function of frequency, doping and temperature. Microwave studies will be undertaken with a novel slow wave device (helical resonator), along with conventional microwave cavities. The scientific objectives are to understand the dynamical conductivity and dielectric response functions of both the localized and itinerant electrons present in barely metallic samples. These microwave studies afford an excellent area for the training of graduate students. This work may also impact our understanding of high temperature superconductivity. ***

3 9803969 Castner 这是一个凝聚态物理项目，将使用螺旋谐振器研究重掺杂半导体 Si:P、Si:As 和其他系统的频率相关输运特性，接近金属-绝缘体转变 (MIT)。螺旋谐振器允许在 100 MHz 至 3 GHz 频率范围内进行测量。对样品引起的频移和品质因数变化的测量将产生有关半导体样品的介电响应和电导率的信息，作为 MIT 附近掺杂剂水平的函数。该项目的主要目标是 (1) 阐明本地化和相互作用校正几乎没有金属样品的复杂介电响应的性质，以便与理论进行比较，(2) 随着温度降低，寻找临界浓度下电导率的异常频率依赖性，以及 (3) 使用传统网络分析仪和微波谐振腔将微波测量扩展到远高于 3 GHz 的频率。另外的研究将涉及锑掺杂硅的电子自旋共振（ESR）线宽的研究。所有这些测量都涉及高度相关电子系统中电导率的一般问题。研究结果将与包括高温超导问题在内的许多相关科学领域相关。该项目让研究生接触基础物理学，并提供多种电气测量技术的经验。与该项目相关的学生为一系列的职业机会做好了准备。 %%% 硅作为当今最重要的电子材料，已被广泛研究了四十多年。当施主或受主的掺杂增加到临界密度以上时，重掺杂硅表现出绝缘体到金属的转变。尽管这种相变的静态输运和热性质已被广泛研究，但对于这种不寻常的相变（其特征为无序、电子-电子相互作用和强电子相关性）仍没有普遍接受的理解。尽管存在一些红外数据，但对金属样品的动态特性作为频率、掺杂和温度的函数的研究还不够。微波研究将使用新型慢波装置（螺旋谐振器）以及传统的微波腔进行。科学目标是了解几乎没有金属的样品中存在的局域电子和巡回电子的动态电导率和介电响应函数。这些微波研究为研究生的培训提供了一个极好的领域。这项工作也可能会影响我们对高温超导的理解。 ***