Unexpected large thermal rectification in asymmetric grain boundary of graphene

We have investigated the lattice thermal transport across the asymmetric tilt grain boundary between armchair and zigzag graphene by nonequilibrium molecular dynamics (NEMD). We have observed significant temperature drop and ultra-low temperature-dependent thermal boundary resistance. More importantly, we find an unexpected thermal rectification phenomenon. The thermal conductivity and Kapitza conductance is direction-dependent. The effect of thermal rectification could be amplified by increasing the difference of temperature imposed on two sides. Our results propose a promising kind of thermal rectifier and phonon diodes based on polycrystalline graphene without delicate manipulation of the atomic structure.

► We investigate thermal transport across asymmetric grain boundary using NEMD. ► Ultra-low temperature-dependent thermal boundary resistance was observed. ► Unexpected ultra-high thermal rectification was discovered. ► The thermal rectification could be tuned by changing temperature difference. ► A new method to design nanoscale thermal rectifier was proposed.