CAREER: Phonon Scattering By Electrons: From Fundamental Understanding To Thermal Transport Control

对能源系统中热传输过程的基本了解和控制对于提高能源效率和社会的可持续性至关重要，因为目前每年超过60%的能源消耗以废热的形式被丢弃。有效控制热传输仍然是一项技术挑战，因为固体材料中的主要热载体通常对外部影响不太敏感。这个CAREER项目研究了一种控制固体热传输的新方法的理论基础和实际可行性：使用外部电磁场来显着改变传热过程。该项目不仅推进了我们对最先进材料和设备的能源传输的基本理解，而且通过提供新的实用策略来设计更高效和可持续的能源系统，使社会受益。这个职业生涯项目还侧重于提高劳动力对下一代可再生能源技术的准备，让K-12和本科生接触动手可再生能源收集项目，并通过为来自代表性不足的少数民族社区的本科研究人员提供研究机会，促进可再生能源领域的多样性。该项目的总体目标是了解声子和电子可以改变固态材料的热传输特性。这个项目的动机是我们最近发现，声子-电子散射可以成为主要的声子散射机制，在室温下具有高电子浓度的半导体。从理论上讲，最先进的第一性原理声子-电子散射计算耦合玻尔兹曼输运方程将被用来理解声子阻尼和放大的声子-电子散射，揭示关键因素，确定强度的声子-电子散射和识别材料与强声子-电子散射潜在的热开关应用。在实验上，将开发超快光学和电子光谱方法，并应用于表征具有不同频率、动量和偏振的声子模式的声子-电子散射强度，并通过外部光激发和静电门控修改声子-电子散射来演示固态热开关。该CAREER项目不仅为高电子浓度器件中的能量转移过程提供了新的见解，还为开发基于微观能量载体相互作用的新型功能能源材料和器件提供了变革性机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Fundamental understanding and control of heat transport processes in our energy systems is crucial to improve the energy efficiency and sustainability of our society, as currently over 60% of our total energy consumption is rejected in the form of waste heat each year. Effective control of the heat transport remains a technological challenge because major heat carriers in solid materials are typically less sensitive to external influence. This CAREER project examines the theoretical basis and practical feasibility of a novel means to control heat transport in solids: using external electromagnetic fields to significantly alter the heat transfer processes. This project not only advances our fundamental understanding of energy transport in state-of-the-art materials and devices, but also benefits the society by providing new practical strategies to design more efficient and sustainable energy systems. This CAREER project also focuses on raising the workforce readiness for next-generation renewable energy technologies by exposing K-12 and undergraduate students to hands-on renewable energy harvesting projects, and promoting the diversity of the renewable energy field by providing research opportunities to undergraduate researchers from underrepresented minority communities.The overarching goal of this project is to understand how the interaction between phonons and electrons can modify the thermal transport properties of solid-state materials. This project is motivated by our recent finding that phonon-electron scattering can become the dominant phonon scattering mechanism in semiconductors with high electron concentrations at room temperature. Theoretically, state-of-the-art first-principles phonon-electron scattering calculation with coupled Boltzmann transport equations will be employed to understand phonon damping and amplification by phonon-electron scattering, reveal key factors that determine the strength of phonon-electron scattering and identify materials with strong phonon-electron scattering for potential thermal switching applications. Experimentally, ultrafast optical and electron spectroscopic methods will be developed and applied to characterize the phonon-electron scattering strength for phonon modes with different frequencies, momenta and polarizations and demonstrate solid-state thermal switching by modifying phonon-electron scattering via external photoexcitation and electrostatic gating. This CAREER project not only generates new insights for energy transfer processes in devices with high electron concentrations, but also provides transformative opportunities to develop novel functional energy materials and devices based on the interaction of microscopic energy carriers.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.