CAREER: Fundamental Investigation of the Wave Nature of Lattice Thermal Transport

热传递是纳米工程的一个限制因素：如果微芯片或激光器等微调元件变得太热或无法控制地传导热量，则设备将无法按预期运行。因此，了解如何在纳米尺度下控制传热在许多工程应用中至关重要。半导体晶体中的热传导由称为声子的集体原子振动控制。通常，声子被视为可以通过材料传播的粒子，从而携带热量，并且可以被材料缺陷或其他声子散射。然而，声子的波动性质可以在由周期性或准周期性布置的组件组成的结构中出现或甚至主导热传导，例如，量子级联激光器由交替的材料层和包含密集封装的纳米晶体管的集成电路制成。在这些结构中，声子的传播可以通过相长干涉来促进或通过相消干涉来停止。本项目旨在探索这些有趣的波动行为，并通过互补的计算和实验技术阐明粒子状和波动状声子之间的转变。这项研究将导致新的工程策略，以最大限度地提高量子级联激光器和集成电路等现代设备的散热，或最大限度地减少热电材料和热障的热传导。该项目将紧密结合研究，教育和外联-包括主题科学展览，新课程开发，实践研究指导以及在线课程和研究工具共享-对K-12，本科生和研究生的STEM教育产生广泛，长期的影响。本计画的研究目标为：1）利用互补的光谱声子分析与声子光谱技术，严格了解周期、准周期与非周期结构中类波声子的输运、散射与定域化;以及2）通过对波状和粒子状声子输运的解耦抑制来最小化晶格热输运，利用机器学习辅助的光谱声子分析和结构优化。对声子的波动性质的拟议研究可以大大推进晶体固体中热输运的知识状态，到目前为止，晶体固体中的热输运主要基于声子的粒子性质。这些知识将使基于声子的波动性质的新型工程策略的开发成为可能，打破各种热传递受限技术的热设计或管理瓶颈。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Heat transfer is a limiting factor in nanoscale engineering: if the finely tuned elements such as microchips or lasers get too hot or conduct heat uncontrollably, the devices will not function as intended. Thus, understanding how to control heat transfer at the nanoscale is critical in many engineering applications. Heat conduction in semiconductor crystals is dominated by collective atomic vibrations known as phonons. Conventionally, phonons are treated as particles that can propagate through a material, thus carrying heat, and can be scattered by material defects or other phonons. However, the wave nature of phonons can emerge or even dominate heat conduction in structures composed of periodically or quasi-periodically arranged components, e.g., quantum cascade lasers made of alternating layers of materials and integrated circuits containing densely packed nano-transistors. In those structures, the propagation of phonons can be promoted by constructive interference or halted by destructive interference. This project aims to explore these intriguing wave behaviors and elucidate the transition between particle-like and wave-like phonons through complementary computational and experimental techniques. This research will lead to novel engineering strategies to maximize heat dissipation in modern devices like quantum cascade lasers and integrated circuits or minimize heat conduction in thermoelectric materials and thermal barriers. This project will tightly integrate research, education, and outreach—including themed science exhibits, new curriculum development, hands-on research mentoring, and online course and research tool sharing—to have a broad, long-term impact on STEM education for K-12, undergraduate, and graduate students. The research objectives of this project are to: 1) rigorously understand the transport, scattering, and localization of wave-like phonons in periodic, quasi-periodic, and aperiodic structures, leveraging complementary spectral phonon analysis and phonon spectroscopy techniques; and 2) minimize lattice thermal transport through decoupled suppression of wave-like and particle-like phonon transport, leveraging machine learning-aided spectral phonon analysis and structure optimization. The proposed research on the wave nature of phonons can greatly advance the state of knowledge of thermal transport in crystalline solids, which has until now been primarily based on the particle nature of phonons. Such knowledge will enable the development of novel engineering strategies based on the wave nature of phonons, breaking the bottleneck of the thermal design or management of various heat transfer-limited technologies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.