Heat flux induced coherent vibration of H-shaped single layer graphene structure
We report an exciting behavior of H-shaped single layer graphene structures subject to a heat flux. H-shaped graphene structures with certain particular dimensions were observed to be able to establish coherent mechanical vibrations in the out-of-plane direction directly from a steady state heat flux flowing from the centerline of the structure towards the two ends. Molecular dynamics (MD) simulation methods together with phonon spectral energy density (SED) analysis techniques were used to obtain the phonon dispersion profiles and identify the low frequency high energy phonon modes. Based on these calculations, we proposed a hypothesis that the mechanical vibration is the result of the superposition of the high energy out-of-plane acoustic (ZA mode) phonons traveling in opposite directions via scattering mechanisms. By using a theoretical model based on the superposition principle, we reproduced the vibrational mode of the graphene structure observed in the MD simulation and verified the proposed hypothesis.