Nanotechnology (Commonwealth Union) – Electronic overheating can lead to the degradation of battery life, slowing of processors, device failure and many others.
The efficient thermal control in solid materials is an essential part of developing the next generation of electronic devices. However, the wave-like behavior of heat transport, known as phonon focusing, had previously only been detected under extremely cold, cryogenic conditions, restricting both its exploration and potential applications.
Researchers at the UCLA Samueli School of Engineering have now shown that phonons — quantum-based atomic vibrations responsible for carrying heat — can form concentrated, directional pathways even at room temperature. Rather than spreading evenly in every direction, heat can be steered along specific routes determined by a material’s crystal arrangement, creating new opportunities for thermal management in advanced electronics and quantum technologies.
The findings, published in Nature Physics, were led by Yongjie Hu, a professor of mechanical and aerospace engineering at UCLA Samueli. The team achieved room-temperature phonon focusing in boron arsenide, a crystalline semiconductor known for its exceptional ability to conduct heat. Unlike conventional cooling approaches that remove heat after it disperses, materials such as boron arsenide could allow heat to be directed along carefully designed paths with nanoscale accuracy — similar to the way optical fibers channel light.
To observe this phenomenon, the researchers developed a high-resolution nanoscale temperature imaging technique. They tested it against conventional materials, and found they could detect the circular patterns of heat distribution typical of regular diffusive conduction. Boron arsenide, in contrast, showed unique beam-like thermal patterns, suggesting that heat was flowing preferentially in certain directions within the crystal structure.
The researchers also demonstrated that heat transport patterns can be precisely controlled by the orientation of the crystal, with various crystal surfaces of boron arsenide producing unique sixfold, eightfold, and fourfold focusing arrangements. Notably, this quantum-based phonon behavior remains observable across distances of about one micrometer and may extend to several tens of micrometers, making it relevant for a wide range of current electronic, photonic, and quantum technologies.
“This is a fundamental observation that enables us to think about thermal management in a new way,” explained Hu, who is the corresponding author of the study and a member of the California NanoSystems Institute at UCLA. “By enabling heat to be guided, focused and redistributed with nanoscale precision at room temperature, the discovery establishes a foundation for quantum thermal engineering.”
Managing heat flow at the atomic scale could help address major thermal challenges in AI hardware, microelectronics, aerospace platforms and other advanced electronic systems, where excessive heat can restrict efficiency, durability and future expansion. Hu noted that this capability may also enable researchers to precisely control interactions between phonons, electrons and other energy carriers, opening new possibilities for emerging quantum computing, communication and sensing technologies.
Earlier studies of phonon focusing were mostly confined to cryogenic environments, typically at temperatures just a few degrees above absolute zero. Under these conditions, phonons can travel over long distances with very little scattering. At normal room temperatures, however, phonons were generally believed to scatter rapidly, losing their wave-like behavior and causing heat to move in a more random, diffusive manner.
The latest findings extend Hu’s earlier work, including his team’s 2018 experimental discovery of boron arsenide. Since then, the group has shown that the material can enable highly efficient thermal interfaces and improved gallium nitride devices by enhancing cooling performance, demonstrating its potential for future semiconductor technologies. Boron arsenide’s exceptionally low phonon scattering allows wave-based heat transport to remain intact even under room-temperature conditions.
The measured heat-distribution patterns closely aligned with theoretical predictions, demonstrating that phonons can move across remarkably long distances without scattering. This extended travel range is essential for allowing wave-like heat transport to occur even at room temperature.
