Minimum thermal conductance in graphene and boron nitride superlattice

The minimum thermal conductance versus supercell size (d(s)) is revealed in graphene and boron nitride superlattice with d(s) far below the phonon mean free path. The minimum value is reached at a constant ratio of d(s)/L approximate to 5%, where L is the thickness of the superlattice; thus, the minimum point of d(s) depends on L. The phenomenon is attributed to the localization property and the number of confined modes in the superlattice. With the increase of d(s), the localization of the confined mode is enhanced while the number of confined modes decreases, which directly results in the minimum thermal conductance. (C) 2011 American Institute of Physics. [doi:10.1063/1.3619832]