  We report a new approach to the thermal conductivity manipulation --
substrate coupling. Generally, the phonon scattering with substrates can
decrease the thermal conductivity, as observed in recent experiments. However,
we find that at certain regions, the coupling to substrates can increase the
thermal conductivity due to a reduction of anharmonic phonon scattering induced
by shift of the phonon band to the low wave vector. In this way, the thermal
conductivity can be efficiently manipulated via coupling to different
substrates, without changing or destroying the material structures. This idea
is demonstrated by calculating the thermal conductivity of modified
double-walled carbon nanotubes and also by the ice nanotubes coupled within
carbon nanotubes.
