Researchers have developed a new technique to suppress radiative heat transfer over micrometric distances, a crucial advance for energy efficiency in nanodevices. Using hexagonal boron nitride (hBN) metasurfaces with engineered dispersion, they have managed to reduce radiative heat flux by a factor of 10 at room temperature. This achievement overcomes the limitations of previous methods, which could only suppress heat in narrow frequency bands or required cryogenic temperatures.

Near-field radiative heat transfer becomes dominant at micrometric and nanometric scales, surpassing conduction and convection. This is particularly relevant in devices such as phase-change memories, hard drives, and thermophotovoltaic cells, where precise heat control is essential for optimal performance. Suppressing this type of heat transfer is challenging due to the evanescent wave nature of the polar plasmonic and phononic modes that mediate transport.

The team designed hBN metasurfaces with a periodic structure that allows for the engineering of polar phonon dispersion. By manipulating the geometry of the patterns, they were able to modify the photonic density of states and, therefore, the radiative heat transfer. Experimental results, validated with simulations, showed up to 90% suppression of radiative heat flux across a broad frequency range, from mid- to far-infrared. This suppression remained effective at room temperature, opening the door for its application in existing technologies.

This breakthrough has significant implications for the design of more efficient and reliable nanometric devices. The ability to control radiative heat so effectively could lead to new generations of thermal management systems, high-performance infrared sensors, and energy harvesting devices. Next steps include integrating these metasurfaces into device prototypes to demonstrate their impact in real-world scenarios and exploring material optimization to achieve even greater suppression.