  The thermal conductivity of graphene nanoribbons (layer from 1 to 8 atomic
planes) is investigated by using the nonequilibrium molecular dynamics method.
We present that the room-temperature thermal conductivity decays monotonically
with the number of the layers in few-layer graphene. The superiority of zigzag
graphene in thermal conductivity is only available in high temperature region
and disappears in multi-layer case. It is explained that the phonon spectral
shrink in high frequency induces the change of thermal conductivity. It is also
reported that single-layer graphene has better ballistic transport property
than the multi-layer graphene.
