Extraordinary Polaritonic Heat Conduction

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Non-technical Abstract: Heat transfer is ubiquitous and plays an important role in our daily lives and industrial processes, such as cooling of computer chips and heating of buildings. In classical textbooks of thermal physics, it is well known that the dominant mode of heat transfer in solids is heat conduction, which is known to be slow (travels at around the speed of sound) and diffusive (non-directional). This project studies a new heat conduction mechanism that combines the light in vacuum and sound in solids to conduct heat at high speed (on the order of speed of light) and with a high degree of directionality. The study is important as it may contribute to diverse applications such as more efficient thermal management of computer chips, light emitting diodes, and buildings. By integrating photonics, thermal science, and nanotechnologies, the project provides an excellent interdisciplinary platform to educate and train female graduate students in physics and engineering and offers attractive hands-on laboratory experience for undergraduate and local high-school students from underrepresented minority groups. Technical Abstract: Heat conduction in solids is normally described as a diffusion process with short mean free path (MFP 10 microns) associated with the main heat carriers, such as phonons and electrons. The goal of this project is to theoretically and experimentally investigate extraordinary thermal transport phenomena in a new regime of heat conduction mediated by surface phonon polariton (SPhP), which originates from the coupling between optical phonon and photon. SPhP is highly confined along the interface between a polar dielectric material and its surroundings and thus can carry high energy flux, comparable to or even higher than that of phonons in a solid. Under suitable conditions, SPhP can have extremely long propagation lengths (mm or longer) even at room and high temperature, and therefore, can exhibit extraordinary behaviors over a much longer distance. The project utilizes novel experimental techniques in nanoscale device fabrication and high-resolution nano-watt calorimetry, combined with rigorous theoretical modeling and numeric simulation, to explore extraordinary SPhP heat conduction phenomena in polar dielectric nanostructures, including low-dimensional heat conduction, non-diffusive and quantum thermal transport, and dynamically tunable thermal transport.This Division of Materials Research (DMR) grant supports research to investigate extraordinary thermal transport phenomena in a new regime of heat conduction mediated by surface phonon polariton with funding from the Condensed Matter Physics (CMP) Program in the DMR of the Mathematical and Physical Sciences Directorate.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.