Engineers at UCLA have shown that heat can travel through a crystal in focused, ray-like beams at room temperature, a quantum effect called phonon focusing that scientists had previously only managed to observe at extreme cryogenic temperatures.
Led by Professor Yongjie Hu, the team tracked phonons — the atomic vibrations that carry heat — moving through boron arsenide in sixfold, eightfold, and fourfold patterns depending on the crystal's orientation, rather than spreading out randomly as heat normally does. The wave-like behavior stayed detectable across a full micrometer and may extend even further, thanks to the material's unusually weak phonon scattering.
"By enabling heat to be guided, focused and redistributed with nanoscale precision at room temperature, the discovery establishes a foundation for quantum thermal engineering," Hu said. The findings, published in Nature Physics, point toward practical uses in cooling AI chips and other microelectronics, where controlling heat with pinpoint accuracy — similar to how optical fibers channel light — could ease one of the industry's biggest bottlenecks.