Thermal resistance by transition between collective and non-collective phonon flows in graphitic materials

TL;DR

This study investigates how normal phonon scattering influences thermal resistance in graphitic materials, revealing significant flux reduction during the transition from non-collective to collective phonon flow, with implications for heat transport modeling.

Contribution

It provides the first detailed analysis of N-scattering effects on thermal resistance during phonon flow transition in graphitic materials using Monte Carlo simulations.

Findings

N-scattering reduces heat flux by up to 40% at 300 K.

The flux reduction is larger than in Debye crystals due to non-linear dispersion.

N-scattering effects are temperature-dependent and more pronounced in graphitic materials.

Abstract

Phonons in graphitic materials exhibit strong normal scattering (N-scattering) compared to umklapp scattering (U-scattering). The strong N-scattering cause collective phonon flow, unlike the relatively common cases where U-scattering is dominant. If graphitic materials have finite size and contact with hot and cold reservoirs emitting phonons with non-collective distribution, N-scattering change the non-collective phonon flow to the collective phonon flow near the interface between graphitic material and a heat reservoir. We study the thermal resistance by N-scattering during the transition between non-collective and collective phonon flows. Our Monte Carlo solution of Peierls-Boltzmann transport equation shows that the N-scattering in graphitic materials reduce heat flux from the ballistic case by around 15%, 30%, and 40% at 100, 200, and 300 K, respectively. This is significantly larger than ~ 5% reduction of Debye crystal with similar Debye temperature (~ 2300 K). We associate the large reduction of heat flux by N-scattering with the non-linear dispersion and multiple phonon branches with different group velocities of graphitic materials.