Strain dependence of the heat transport properties of graphene nanoribbons

TL;DR

This study investigates how tensile strain influences the ballistic thermal conductance of graphene nanoribbons, revealing temperature-dependent effects and underlying atomistic mechanisms through advanced computational methods.

Contribution

It provides a detailed atomistic analysis of strain effects on heat transport in graphene nanoribbons using density-functional theory and Green's function methods, highlighting temperature-dependent behaviors.

Findings

Low-temperature conductance increases due to out-of-plane acoustic modes.

High-temperature conductance decreases with tensile strain.

Lattice constants show a three-family behavior based on ribbon width.

Abstract

Using a combination of accurate density-functional theory and a nonequilibrium Green function's method, we calculate the ballistic thermal conductance characteristics of tensile-strained armchair (AGNR) and zigzag (ZGNR) edge graphene nanoribbons, with widths between 3-50 \AA. The optimized lateral lattice constants for AGNRs of different widths display a three-family behavior when the ribbons are grouped according to N modulo 3, where $N$ represents the number of carbon atoms across the width of the ribbon. Two lowest-frequency out-of-plane acoustic modes play a decisive role in increasing the thermal conductance of AGNR-N at low temperatures. At high temperatures the effect of tensile strain is to reduce the thermal conductance of AGNR-N and ZGNR-N. These results could be explained by the changes in force constants in the in-plane and out-of-plane directions with the application of strain. This fundamental atomistic understanding of the heat transport in graphene nanoribbons paves a way to effect changes in their thermal properties via strain at various temperatures.