Minimum thermal conductance in graphene and boron nitride superlattice

TL;DR

This study investigates the behavior of thermal conductance in graphene and boron nitride superlattices, revealing a minimum conductance point related to supercell size and mode localization effects.

Contribution

It identifies the conditions for minimum thermal conductance in superlattices and explains the underlying localization mechanism affecting phonon transport.

Findings

Minimum thermal conductance occurs at a supercell size ratio of about 5%.

The minimum conductance depends on the total superlattice length.

Localization of confined phonon modes influences conductance behavior.

Abstract

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 $d_{s}/L\approx 5%$, where $L$ is the total length 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.