Remarkable thermal rectification in pristine and symmetric monolayer graphene enabled by asymmetric thermal contact

Thermal rectification is a nonreciprocal thermal transport phenomenon, which typically takes place in asymmetric structures or hetero-junctions. In this work, we propose a new route to achieve remarkable thermal rectification even in pristine single-layer graphene without asymmetry by engineering the thermal contacts at the two ends. When setting a fixed long thermal contact at one end and varying the length of thermal contact at the other end, our molecular dynamics simulations demonstrate that notable thermal rectification efficiency can be achieved with very short thermal contact, which vanishes in the limit of long thermal contact. Such a strategy of asymmetric thermal contact can provide a significant enhancement of thermal rectification efficiency, achieving around 920% thermal rectification in the short sample with a length of 200nm and around 110% thermal rectification in the micrometer scale sample. Phonon participation ratio analysis reveals that the strong localization of low-frequency acoustic phonons is induced by the short thermal contact in the backward direction, leading to a significant temperature jump at the short thermal contact in the backward direction and thus the thermal rectification in pristine single-layer graphene. Our study provides a new path to achieve notable thermal rectification even in the symmetric structures by engineering the thermal contact.