Strain gradient induced thermal rectification in graphene

Thermal rectification (TR) has attracted significant research interest due to its potential to achieve active heat control in various nanoscale applications. In this study, we propose a novel graphene-based thermal rectifier under a strain gradient. Two kinds of strain gradients, namely, compressive and tensile, are considered. We observe that under a compressive strain gradient (CSGG), the heat flows preferentially from the high-compressed region to the lower, with a significant TR of 120%. But for a tensile strain gradient (TSGG), the direction of TR is dependent on its length. For a smaller system, the TR occurs from the high-strained to low-strained region, while for larger systems, the direction of TR is reversed. The strength and location of the standing wave in conjunction with the mismatch in the overlap of the density of states in forward and reverse bias are found to induce TR in TSGG and CSGG. The TR direction is observed to be altered by changing the location of the strain gradient. Additionally, we propose a series thermal rectifier by coupling graphene under strain gradient to asymmetric defective graphene (ADG). A significant increase in the series thermal rectifier is observed when compared to TR in ADG. Our results demonstrate the applicability of strain gradient as a feasible approach to control the thermal rectification ratio and its direction for various applications such as phononic devices and thermal logic circuits.