Thermal conductivity and nonreciprocity in wrinkled monolayer graphene ring

We explore an external tunable approach to produce thermal nonreciprocity, by means of controlling wrinkle characteristics in graphene rings. The wrinkling formation and evolution law of graphene rings under torsional deformation is studied. Results show that wrinkle patterns of monolayer graphene can be flexibly tuned by controlling mechanical torsion. We further study the dependence of graphene rings' thermal conductivity on sizes, temperatures and torsional angles, and reveal the influential mechanism by phonon density of states. Specifically, the thermal conductivity is reduced by 20.4 % when the torsional angle increases from theta = 0 circle to theta = 10.3 circle. Finally, nonreciprocal conductive heat transfer is demonstrated in torsion-wrinkled graphene rings. It is found that thermal nonreciprocity effect is dependent on both torsional angles and temperature differences, i.e., the thermal nonreciprocity factor increase from 1.9 % to 4.5 % as temperature difference varies from 100 K to 400 K under torsional angle theta = 6.9 circle. Our work paves new avenues for the design and implementation of thermal metadevices by mechanical tuning approach.