The effect of structural asymmetry on thermal rectification in nanostructures

Three SWCNT-graphene nanostructure-based models are designed to probe the thermal rectification caused by the structural asymmetry in the boundary thermal contacts, the device, and the whole system, respectively. We find that both the asymmetry of entire system and the asymmetry of the device are not necessary condition for the existence of thermal rectification, and the asymmetry in boundary thermal contacts is more important than the asymmetry in device toward determining both the magnitude and the direction of thermal rectification. Interestingly, notable thermal rectification can exist in the systems with overall structural symmetry when the boundary thermal contacts are structurally asymmetric. Moreover, nanostructures with a structurally symmetric device and structurally asymmetric boundary thermal contacts can still display significant thermal rectification. These findings could offer insight into the future design and performance improvement of nanostructured thermal rectifiers.