Efficient heat management in solids is key to advancing the next generation of electronics. However, wave-like heat movement—known as phonon focusing—had been observed only at extremely low, or cryogenic, temperatures, limiting its study and practical use.

Now, researchers at the UCLA Samueli School of Engineering have demonstrated that phonons, atomic heat-carrying vibrations with quantum properties, can travel in focused, raylike paths at room temperature. Instead of spreading uniformly in all directions, heat can move along guided pathways defined by a material’s crystal structure, opening new possibilities for managing heat flow in future electronics and quantum technologies.