  Kirigami structure, from the macro- to the nanoscale, exhibits distinct and
tunable properties from original 2-dimensional sheet by tailoring. In present
work, the extreme reduction of the thermal conductivity by tailoring sizes in
graphene nanoribbon kirigami (GNR-k) is demonstrated using nonequilibrium
molecular dynamics simulations. The results show that the thermal conductivity
of GNR-k (around 5.1 Wm-1K-1) is about two orders of magnitude lower than that
of the pristine graphene nanoribbon (GNR) (around 151.6 Wm-1K-1), while the
minimum value is expected to be approaching zero in extreme case from our
theoretical model. To explore the origin of the reduction of the thermal
conductivity, the micro-heat flux on each atoms of GNR-k has been further
studied. The results attribute the reduction of the thermal conductivity to
three main sources as: the elongation of real heat flux path, the
overestimation of real heat flux area and the phonon scattering at the vacancy
of the edge. Moreover, the strain engineering effect on the thermal
conductivity of GNR-k and a thermal robustness property has been investigated.
Our results provide physical insights into the origins of the ultralow and
robust thermal conductivity of GNR-k, which also suggests that the GNR-k can be
used for nanaoscale heat management and thermoelectric application.
