Thermal conductance of graphene and dimerite

TL;DR

This paper studies the phonon thermal conductance of graphene, revealing weak directional dependence due to symmetry and showing increased anisotropy in a symmetry-broken form called dimerite.

Contribution

It provides a theoretical analysis of how symmetry affects thermal conductance in graphene and introduces dimerite as a material with enhanced anisotropic thermal properties.

Findings

Thermal conductance varies weakly with direction, with a period of π/3.

Symmetry breaking in graphene enhances anisotropic thermal conductance.

Group velocities of phonon modes are key to directional dependence.

Abstract

We investigate the phonon thermal conductance of graphene regarding the graphene sheet as the large-width limit of graphene strips in the ballistic limit. We find that the thermal conductance depends weakly on the direction angle $\theta$ of the thermal flux periodically with period $\pi/3$. It is further shown that the nature of this directional dependence is the directional dependence of group velocities of the phonon modes in the graphene, originating from the $D_{6h}$ symmetry in the honeycomb structure. By breaking the $D_{6h}$ symmetry in graphene, we see more obvious anisotropic effect in the thermal conductance as demonstrated by dimerite.