  In the present molecular dynamics study, external ac driving is used at
frequencies outside the phonon spectrum to excite gap DBs in uniformly strained
graphene nanoribbon. Harmonic displacement or harmonic force is applied to a
zigzag atomic chain of graphene. In the former case non-propagating DBs are
excited on the atoms next to the driven atoms, while in the latter case the
excited DBs propagate along the nanoribbon. The energy transfer along the
nanoribbon assisted by the DBs is investigated in detail and the differences
between harmonic displacement driving and harmonic force driving are discussed.
It is concluded that the amplitude of external driving at out of phonon
spectrum frequencies should not necessarily be large to obtain a noticeable
energy transfer to the system. Overall, our results suggest that external
harmonic driving even at relatively small driving amplitudes can be used to
control excitation of DBs and consequently the energy transfer to the system.
