CAREER: Quantum Size Effects on Thermal Radiation

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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.