  Thermal transport in nanoribbon based nanostructures is critical to advancing
its applications. Wave effects of phonons can give rise to controllability of
heat conduction in nanostructures beyond that by particle scattering. In this
paper, by introducing pillars to form structural resonance, we systematically
studied the thermal conductivity of graphene nanoribbon based phononic
metamaterials (GNPM) through non-equilibrium molecular dynamical simulation.
Interestingly, it is found that the thermal conductivity of GNPM is counter
intuitively enhanced by isotope engineering, which is strong contrast to the
common notion that isotope engineering reduces thermal conductivity.Further
mode analysis and atomic Green function calculation reveal that the unexpected
increasing in thermal conductivity originates from the breaking of the resonant
hybridization wave effect between the resonant modes and the propagating modes
induced by isotope engineering. Besides, factors including the system width and
pillar height can also efficiently tune the thermal conductivity of GNPM. This
abnormal mechanism provides a new dimension to manipulate phonon transport in
nanoribbon based nanostructures through wave effect.
