Length and torsion dependence of thermal conductivity in twisted graphene nanoribbons

Research on the physical properties of materials at the nanoscale is crucial for the development of breakthrough nanotechnologies. One of the key properties to consider is the ability to conduct heat, i.e., its thermal conductivity. Graphene is a remarkable nanostructure with exceptional physical properties, including one of the highest thermal conductivities (TCs) ever measured. Graphene nanoribbons (GNRs) share most fundamental properties with graphene, with the added benefit of having a controllable electronic bandgap. One method to achieve such control is by twisting the GNR, which can tailor its electronic properties, as well as change their TCs. Here, we revisit the dependence of the TC of twisted GNRs (TGNRs) on the number of applied turns to the GNR by calculating more precise and mathematically well defined geometric parameters related to the TGNR shape, namely, its twist and writhe. We show that the dependence of the TC on twist is not a simple function of the number of turns initially applied to a straight GNR. In fact, we show that the TC of TGNRs requires at least two parameters to be properly described. Our conclusions are supported by atomistic molecular dynamics simulations to obtain the TC of suspended TGNRs prepared under different values of initially applied turns and different sizes of their suspended part. Among possible choices of parameter pairs, we show that TC can be appropriately described by the initial number of turns and the initial twist density of the TGNRs.