Thermal Resistance by Transition Between Collective and Non-Collective Phonon Flows 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.

KEYWORDS:

• phonon
• Boltzmann transport theory
• Monte Carlo method
• graphitic materials

Acknowledgments

We acknowledge support from National Science Foundation (Award Nos. 1705756 and 1709307). The simulation was performed using the Linux clusters of Extreme Science and Engineering Discovery Environment (XSEDE) through allocation TG-CTS180043 and Center for Research Computing at the University of Pittsburgh. S.L. thank L. Lindsay for providing the phonon dispersion of SWCNTs.

Additional information

Funding

This work was supported by the National Science Foundation [1705756, 1709307].