Researchers show that heat spreads as a wave through graphene

The dissipation of heat through two-dimensional materials such as graphene is through wave-like diffusion. This is demonstrated by researchers from the EPFL in Switzerland. This outcome can be used in future research into the use of graphene for electronics.

The research, which appeared in Nature Communications, is important because as components become smaller and smaller, it is increasingly difficult to get rid of heat quickly enough. One solution is to use materials that have a very high thermal conductivity to dissipate the heat quickly, such as graphene. Because heat behaves differently in materials only a few atoms thick, the question of how the heat is distributed must first be answered properly.

The researchers showed that heat spreads in the form of a wave. This phenomenon had been observed before, but only at temperatures near absolute zero, according to a report on the EPFL site.

Two-dimensional materials react differently to heat than three-dimensional ones. They have the property of transporting heat with extremely little loss, even at room temperature. Normally, heat moves through crystalline materials via vibrating atoms. This mode of vibration is called a phonon. As heat travels through a three-dimensional material, those phonons continue to collide. All these processes ensure that the conductivity of the material decreases over longer distances. Only under extreme conditions, when the temperature approaches absolute zero, is it possible to conduct heat with virtually no loss.

The EPFL researchers show that materials react very differently in two-dimensional form. Even at room temperature it appears that heat can be conducted almost without loss. This is caused by a phenomenon called ‘second sound’, where heat moves through a material in a wave-like motion rather than through the more mechanical diffusion. Via the second sound, the phonons move simultaneously over great distances.