Dimensional crossover of thermal conductance in graphene nanoribbons: A first-principles approach

TL;DR

This study uses first-principles calculations to explore how thermal conductance in graphene nanoribbons transitions from one-dimensional to two-dimensional behavior as the ribbon width increases, providing insights into thermal transport properties.

Contribution

It demonstrates the dimensional crossover of thermal conductance in GNRs using a first-principles approach and derives a heuristic model for this transition.

Findings

Thermal conductance exhibits a $T^{1.5}$ dependence at low temperatures for narrow GNRs.

The crossover from 1D to 2D thermal behavior is clearly demonstrated with increasing ribbon width.

Estimated thermal conductivity values at room temperature for GNRs and graphene sheets.

Abstract

First-principles density-functional calculations are performed to investigate the thermal transport properties in graphene nanoribbons (GNRs). The dimensional crossover of thermal conductance from one to two dimensions (2D) is clearly demonstrated with increasing ribbon width. The thermal conductance of GNRs in a few nanometer width already exhibits an approximate low-temperature dependence of $T^{1.5}$, like that of 2D graphene sheet which is attributed to the quadratic nature of dispersion relation for the out-of-plane acoustic phonon modes. Using a zone-folding method, we heuristically derive the dimensional crossover of thermal conductance with the increase of ribbon width. Combining our calculations with the experimental phonon mean-free path, some typical values of thermal conductivity at room temperature are estimated for GNRs and for 2D graphene sheet, respectively. Our findings clarify the issue of low-temperature dependence of thermal transport in GNRs and suggest a calibration range of thermal conductivity for experimental measurements in graphene-based materials.