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

3 9803969 Castner这是一个凝聚态物理学项目，将使用螺旋谐振器研究重掺杂半导体Si：P，Si：As和其他系统的频率依赖输运特性，接近金属-绝缘体转变（MIT）。螺旋谐振器允许在100 MHz至3 GHz的频率范围内进行测量。样品引起的频率偏移和品质因数变化的测量将产生关于半导体样品的介电响应和电导率作为MIT附近的掺杂剂水平的函数的信息。该项目的主要目标是（1）澄清纯金属样品复杂介电响应的局部化和相互作用校正的性质，以便与理论进行比较，（2）寻找临界浓度下电导率随温度降低的不寻常频率依赖性，以及（3）使用常规网络分析仪和谐振微波腔将微波测量扩展到远高于3GHz的频率。此外，还将研究掺锑硅的电子自旋共振（ESR）线宽。所有这些测量都与高度关联电子系统中的电导率的一般问题有关。这些结果将与包括高温超导问题在内的一些相关科学领域有关。该项目使研究生接触基础物理学，并提供一些电气测量技术的经验。与该项目相关的学生准备了一系列的职业机会。硅作为当今最重要的电子材料，已经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。虽然这种相变的静态输运和热性质已经被广泛研究，但仍然没有普遍接受的理解这种不寻常的相变，其特征是无序，电子-电子相互作用和强电子相关。虽然存在一些红外数据，但对金属样品作为频率、掺杂和温度的函数的动力学性质的研究还不够。微波研究将与一种新型的慢波器件（螺旋谐振器），沿着与传统的微波腔。科学的目标是了解动态电导率和介电响应函数的本地化和巡回电子存在于勉强金属样品。这些微波研究为研究生的培养提供了一个很好的领域。这项工作也可能影响我们对高温超导性的理解。***

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. ***