  We employ a semi-classical Langevin approach to study current-induced atomic
dynamics in a partially dehydrogenated armchair graphene nanoribbon. All
parameters are obtained from density functional theory. The dehydrogenated
carbon dimers behave as effective impurities, whose motion decouples from the
rest of carbon atoms. The electrical current can couple the dimer motion in a
coherent fashion. The coupling, which is mediated by nonconservative and
pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby
show their signature in this simple system. We study the atomic dynamics and
current-induced vibrational instabilities using a simplified eigen-mode
analysis.Our study shows that the armchair nanoribbon serves as a possible
testbed for probing the current-induced forces.
