CAREER: Nanoscale Phonon Spectrometer to Quantitatively Characterize Low-Dimensional Heat Transfer

****技术摘要****本学院早期职业发展（Career）项目的实验旨在通过纳米尺度几何研究热流的基础科学。该项目旨在阐明声子行为的关键模型预测，如表面散射的波长依赖性和复杂纳米级几何形状选择性阻挡、增强或直接热流的能力。这将通过开发一种探测纳米结构中单频声子传输的装置来实现。利用超导隧道结（stj）可以产生可控能量的声子。通过结注入激发态电子导致声子在随后的弛豫和电子重新组合到库珀对基态时发射。同样的原理将被用于stj的声子探测：入射声子在探测器中破坏库珀对，产生可测量的隧道电流。成功的测量将引起纳米材料、热输运和超导器件领域研究人员的广泛兴趣。该项目将支持培养一名纳米制造、低温和敏感测量技术方面的研究生。它将教育学生广泛的当代物理研究领域，包括超导器件和声子输运。这项研究还将被纳入一个新的扩展模块，促进学生的科学学习和对纳米技术的更广泛理解。****非技术摘要****在绝缘材料中，热量通过原子振动（“声子”）传播，它像水中的涟漪或空气中的声波一样在固体中传播，但速度要快得多。现有的物理理论很好地解释了块状物质中的热传递；然而，当同样的材料缩小到只有几千个原子宽时，这些定律就失效了。理论模型预测了纳米结构的非凡行为——比如仅仅基于纳米结构形状的选择性热波传输——但是这些想法还没有被实验量化。这个学院早期职业发展（Career）项目将通过构建纳米级设备来创建和探测原子振动传热来研究纳米级热传递。这项工作将通过利用纳米材料不同寻常的热特性，为热电和微电子冷却模块等设备的改进工程提供信息。由于最新的先进纳米制造技术，这项工作最近才成为可能。该项目将支持一名研究生在相关尖端纳米制造、低温和敏感测量技术方面的培训。它将教育学生广泛的当代物理研究领域，包括超导器件和声子输运。此外，这项研究将被纳入一个新的扩展模块，促进学生的科学学习和对纳米技术的更广泛理解。

****TECHNICAL ABSTRACT****The experiments in this Faculty Early Career Development (CAREER) project aim to study the fundamental science of heat flow through nanoscale geometries. The project intends to elucidate key model predictions of phonon behavior, such as the wavelength dependence of surface scattering and the ability of complex nanoscale geometries to selectively block, enhance, or direct heat flow. This will be accomplished by developing a device for probing single-frequency phonon transmission in nanostructures. Phonons of controlled energy will be generated by using superconducting tunnel junctions (STJs). Injection of excited-state electrons through the junction causes emission of phonons during the subsequent relaxation and recombination of the electrons into the Cooper-pair ground state. The same principle will be used for phonon detection by STJs: incident phonons break Cooper pairs in the detector, creating a measurable tunnel current. Successful measurements will be of broad interest to researchers in the fields of nanomaterials, thermal transport, and superconducting devices. The project will support the training of a graduate student in nanofabrication, cryogenics, and sensitive measurement techniques. It will educate the student in a broad range of contemporary physics research areas, including superconducting devices and phonon transport. The research will also be incorporated into a new outreach module promoting science learning to students and a broader understanding of nanotechnology. ****NON-TECHNICAL ABSTRACT****In insulating materials, heat is transmitted by atomic vibrations ('phonons'), which move through a solid like ripples in water or sound waves in air, but much more rapidly. Existing physical theories explain heat transport well in bulk materials; however, these laws break down when the same material is reduced to only a few thousand atoms wide. Theoretical modeling predicts remarkable behaviors for nanostructures - such as the selective transmission of heat waves based solely on the nanostructure's shape - but these ideas have not been experimentally quantified. This Faculty Early Career Development (CAREER) project will study nanoscale heat transport by building a nano-sized device to create and probe atomic vibrational heat transfer. This work will inform improved engineering of devices like thermoelectrics and microelectronic cooling modules through the exploitation of nanomaterials' unusual thermal properties. This work has only recently been made possible due to newly available advanced nanofabrication techniques. The project will support the training of a graduate student in related cutting-edge nanofabrication, cryogenics, and sensitive measurement techniques. It will educate the student in a broad range of contemporary physics research areas, including superconducting devices and phonon transport. In addition, the research will be incorporated into a new outreach module promoting science learning to students and a broader understanding of nanotechnology.