Electronic Thermal Transport in Nanoscale Conductors

0933454Shi描述电子热输运的Wiedemann-Franz（W-F）定律是索末菲理论成功的标志。然而，对于限制在一维或二维纳米结构中的电子，一些有趣的现象可能导致W-F定律的崩溃。这些现象包括与增加的电子-电子相互作用相关的强相关效应，以及电子局域化。智力优势。这项实验研究解决了一个基本问题，即Wiedemann-Franz定律在低维导体中是否有效。正在解决的科学问题具有非常根本的性质，并且将影响多个学科。实验研究探讨了铜纳米线，准一维聚乙炔纳米纤维和二维石墨烯纳米带中的电子热输运。这些纳米结构的热导率，电导率和塞贝克系数测量使用纳米制造的悬浮测量装置在各种温度下。化学掺杂，电场效应，和热霍尔效应的调谐和确定的电子热导率和隔离的晶格贡献。通过分析测量的洛伦兹数及其温度依赖性，并将测量结果与不同输运理论的预测进行比较，检验了W-F定律的有效性。更广泛的影响。感兴趣的纳米结构正在考虑用于纳米电子学，传感器，能量转换和热管理应用，所有这些都将受益于更好地了解这些纳米结构中的电子热传输。这项研究为研究生和本科生提供了跨学科的教育机会。正在为热科学研究生和本科生课程编写新的示范材料，为三个K-12外联活动编写新的材料，这些活动旨在吸引年轻女孩从事工程专业，并使得克萨斯州的公立学校学生和教师了解工程原理。

0933454ShiThe Wiedemann-Franz (W-F) law describing thermal transport by electrons is a hallmark of success of the Sommerfeld theory. For electrons confined in one- or two-dimensional nanostructures, however, several intriguing phenomena can lead to the breakdown of the W-F law. These phenomena include strong correlation effects associated with increased electron-electron interaction, as well as electron localization. Intellectual Merit. This experimental study addresses a fundamental question regarding whether the Wiedemann-Franz Law is valid in low dimensional conductors. The scientific question being addressed is of a very fundamental nature, and one that will impact multiple disciplines. The experimental study examines electronic thermal transport in copper nanowires, quasi one-dimensional polyacetylene nanofibers, and two-dimensional graphene nanoribbons. The thermal conductivity, electrical conductivity, and Seebeck coefficient of these nanostructures are measured using nanofabricated suspended measurement devices at various temperatures. Chemical doping, electrical field effects, and the thermal Hall effect are employed to tune and determine the electronic thermal conductivity and isolate the lattice contribution. The validity of the W-F law is examined by analyzing the measured Lorenz number and its temperature dependence, and comparing the measurement results with the predictions of different transport theories. Broader Impacts. The nanostructures of interest are being considered for nanoelectronics, sensors, energy conversion, and thermal management applications, all of which will benefit from a better understanding of electronic thermal transport in these nanostructures. The research provides interdisciplinary education opportunities for graduate and undergraduate students. New example materials for a graduate and an undergraduate course in thermal science are being produced, as are new materials for three K-12 outreach activities designed to attract young girls to engineering professions, and to expose public school students and teachers in Texas to engineering principles.