Scientists at UCLA’s Samueli School of Engineering have identified a method for directing heat through crystalline materials using quantum phonon behavior at room temperature, according to findings published in Nature Physics. The research, led by mechanical engineering professor Yongjie Hu, demonstrates that atomic vibrations carrying heat can move through concentrated, ray-shaped paths rather than dispersing uniformly in all directions.
The team studied boron arsenide, a semiconductor with high thermal conductivity, and developed techniques to map temperature at the nanoscale. Temperature measurements revealed distinct ray-shaped patterns aligned with specific crystal directions. When crystal orientation changed, the heat flow patterns shifted in predictable ways, producing sixfold, eightfold, and fourfold focusing patterns. The quantum phonon behavior remained observable across distances of one micrometer and potentially extends to tens of micrometers, a range suitable for electronic, photonic, and quantum device applications.
Previously, phonon focusing had only been observed at cryogenic temperatures near absolute zero. At room temperature, phonons typically scatter frequently and lose the coherence necessary for wave-based heat transport. Boron arsenide exhibits unusually weak phonon scattering, allowing wave-based heat transmission to persist at standard temperatures. Experimental results aligned closely with theoretical calculations, confirming that phonons in the material travel longer distances before scattering.
The capability to control heat at atomic levels could address thermal management challenges in artificial intelligence hardware, microelectronic devices, aerospace systems, and other technologies where overheating reduces performance and reliability. The discovery may also enable adjustment of phonon interactions with electrons and other energy carriers, potentially supporting advances in quantum information systems and sensing technologies. The research builds on earlier work identifying boron arsenide in 2018 and subsequent development of thermal interfaces and gallium nitride devices using the material for cooling applications.
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