CAREER: Quantum Size Effects on Thermal Radiation

量子尺度（即，纳米和亚纳米尺度）材料表现出显著不同于普通块体材料的热辐射性质。这种现象是由材料的电子能带结构在量子尺度上的变化引起的。量子材料的热辐射可以被设计用于使用纳米间隙热光电转换器的高效废热回收以及辐射冷却和智能窗户。此外，量子尺度的热辐射对晶体管和超紧凑电子器件的热管理具有显著影响。尽管如此，热辐射如何在量子水平上发射和交换还没有很好的理解。这个项目将阐明量子体系中热辐射的基本机制。这项研究可能会导致能源收集和保护方面的技术突破。这将通过节约有限的能源资源和保护环境来影响社会。残疾学生、来自缅因州农村地区的女学生和高中教师将直接参与这项研究。主要研究人员的部门将开发一门新的课程和三个关于辐射传热的实验室课程。首先，量子材料的光学和电子（以及因此的热辐射）性质（即，以原子长度尺度设计的材料）可以与体材料显著不同。这为设计具有超出波动电动力学范围的定制热辐射特性的材料提供了一个很好的机会。其次，原子长度尺度的辐射热传递可以在晶体管、超紧凑电路、量子计算机、太阳能电池和医学成像仪等设备的热管理中发挥重要作用。在原子尺度的分离间隙中，出现了诸如声子和电子隧穿的量子尺寸效应。与波动电动力学预测相比，这些效应可以修改辐射传热。虽然已经研究了声子隧穿对两种电介质之间的辐射传热的影响，但是在电子隧穿存在下金属介质之间的辐射传热还没有完全理解。本研究计画将透过下列步骤来阐明量子尺寸对热辐射的影响：（1）建立量子材料热辐射模型的理论架构;（2）不同尺寸量子材料热辐射的理论研究;（3）实验验证量子尺寸对热辐射强度与光谱的影响;（4）研究电子隧穿对量子尺度分离间隙辐射传热的影响，本项目由热输运过程计划和刺激竞争研究既定计划（EPSCoR）联合资助该奖项反映了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。

Quantum-scale (i.e., nanometer and sub-nanometer scale) materials exhibit thermal radiation properties that are significantly different from ordinary bulk materials. This phenomenon is caused by the change in the electronic band structure of the materials at the quantum scale. Thermal radiation of quantum materials can be engineered for highly efficient waste heat recovery using nano-gap thermophotovoltaics as well as for radiative cooling and smart windows. Additionally, thermal radiation at the quantum scale has significant impact on thermal management of transistors and ultra-compact electronics. Despite this significance, how thermal radiation is emitted and exchanged at the quantum level is not well understood. This project will elucidate the fundamental mechanisms underlying thermal radiation in the quantum regime. This research can lead to technological breakthroughs in energy harvesting and conservation. This will impact society by conserving limited energy resources and protecting the environment. Students with disabilities, female students from rural areas of Maine, and high school teachers will be directly involved in this research. A new course and three lab sessions on radiative heat transfer will be developed at the principal investigator’s department.Quantum size effects on thermal radiation are significant for two chief reasons. First, optical and electronic (and thus thermal radiative) properties of quantum materials (i.e., materials that are engineered at the atomic length scale) can differ drastically from bulk materials. This opens up a great opportunity for designing materials with tailored thermal radiative properties beyond the fluctuational-electrodynamics regime. Second, radiative heat transfer at the atomic length scale can play a significant role in thermal management of devices such as transistors, ultra-compact circuits, quantum computers, solar cells, and medical imagers. At atomic scale separation gaps, quantum size effects such as phonon and electron tunneling arise. These effects can modify radiative heat transfer compared to the fluctuational electrodynamics predictions. Although the effect of phonon tunneling on radiative heat transfer between two dielectric media has been studied, radiative heat transfer between metallic media in the presence of electron tunneling is not fully understood. This research project will elucidate quantum size effects on thermal radiation by (1) establishing a theoretical framework for modeling thermal radiation of quantum materials, (2) a theoretical study of thermal radiation by quantum materials of different dimensions, (3) experimental demonstration of quantum size effects on the magnitude and the spectrum of thermal emission, and (4) studying the effect of electron tunneling on radiative heat transfer at quantum-scale separation gaps.This project is jointly funded by the Thermal Transport Processes Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.