Unusual thermal conductivity behavior of serpentine graphene nanoribbons under tensile strain

Thermal conductivity of graphene nanoribbons usually decreases quickly with the increase of tensile strain due to the softened phonon modes and increased lattice anharmonicities. In this work, we present a new design of graphene nanoribbon structures-serpentine graphene nanoribbons (SGNRs) and demonstrate that thermal conductivity of SGNRs increases with the increase of tensile strain through nonequilibrium molecular dynamics (NEMD) simulations. This increase can be held till to as large as 54.7% stretchability of SGNRs. The unusual response of thermal conductivity results from the competition between the elongation of heat transfer path and stress distribution in nanoribbon structures under tension and is closely related with the maximum stretchability of serpentine structures. Both mechanical stress distribution and phonon spectrum of SGNRs are examined to understand the underlying thermal transport mechanism, and show good agreement with simulation findings.