On the highway of heat transfer, thermal energy is traditionally moved through quantum particles known as phonons. However, in today’s nanoscale semiconductors, the efficacy of phonons in removing heat has reached its limit. This limitation has led researchers at Purdue University to focus on harnessing the potential of a novel type of quasiparticles called “polaritons” in order to open a new lane on the heat transfer highway.
In the realm of energy transfer, Thomas Beechem, an associate professor of mechanical engineering, finds himself passionately discussing heat transfer. He describes energy in its various forms, including light and heat, in terms of particles. While photons represent light particles and phonons symbolize heat waves, the emergence of polaritons depicts a unique hybrid of both energy forms. Beechem compares it to a Toyota Prius, an energy carrier that retains some of the properties of both photons and phonons while creating its distinct energy exchange wave.
While polaritons have found their niche in various optical applications, their significant impact on heat transfer has remained largely unexplored until recently. Their potential to effectively move heat becomes noteworthy only when dealing with nanoscale materials. As Jacob Minyard, a Ph.D. student in Beechem’s lab explains, semiconductors have evolved to become increasingly smaller and complex, creating an urgent need to address the inefficiencies of phonons in heat dispersion at nanoscale levels. The researchers’ groundbreaking findings have been published as a Featured Article in the Journal of Applied Physics.
Beechem proudly emphasizes that their research has paved the way for a whole new lane on the heat transfer highway, particularly as semiconductors continue to shrink in size. Recognizing that polaritons dominate heat transfer on any surface thinner than 10 nanometers, the potential for this alternative energy exchange pathway becomes increasingly valuable. By effectively capitalizing on polariton-friendly designs, chip manufacturers can optimize heat conductivity in nanoscale semiconductors. This requires a comprehensive understanding of the involved materials, ranging from the silicon itself to the dielectrics and metals that make up the chip.
While the current research is theoretical, Beechem and Minyard aim to demonstrate to chip manufacturers the practicality of incorporating polariton-based nanoscale heat transfer principles into physical chip designs. This includes considering the physical properties of the materials used, as well as the shape and thickness of the various layers in the chip. As they delve further into this field, they anticipate conducting physical experiments to validate their theoretical findings.
Purdue University provides a vibrant platform for Beechem and Minyard’s research due to its robust heat transfer community. Collaborative discussions with experts like Xianfan Xu, who pioneered experimental realizations of polariton effects, and Xiulin Ruan, a pioneer in phonon scattering, offer invaluable insights. Additionally, the state-of-the-art facilities at the Birck Nanotechnology Center enable the duo to conduct nanoscale experiments and employ unique measurement tools to confirm their findings.
The marrying of photons and phonons into polaritons has unlocked a new era in nanoscale heat transfer. By capitalizing on the unique properties of polaritons, researchers are now able to address the limitations of phonons in removing heat in nanoscale semiconductors. This opens doors to optimized heat conductivity in increasingly small and complex chip designs. As the study of polaritons expands, it promises to deliver practical solutions for chip manufacturers to incorporate efficient nanoscale heat transfer mechanisms into their physical chip designs.