Revisiting thermal conductivity and interface conductance at the nanoscale

TL;DR

This paper introduces a semi-analytical model for nanoscale thermal transport that accurately describes out-of-equilibrium effects and interface conductance, bridging diffusive and ballistic regimes with minimal parameters.

Contribution

The authors develop a novel formalism based on pseudo local temperatures to model heat transfer in nanostructures, including hetero-structures, using only two intrinsic parameters.

Findings

Accurately reproduces Monte Carlo simulation results across all phonon transport regimes.

Effectively models thermal interface conductance at the nanoscale.

Provides insights for interpreting experimental thermal measurements.

Abstract

A semi-analytical model for studying thermal transport at the nanoscale, able to accurately describe both the effect of out of equilibrium transport and the thermal transfer at interfaces, is presented. Our approach is based on the definition of pseudo local temperatures distinguishing the phonon populations according to the direction of their velocity. This formalism leads to a complete set of equations capturing the heat transfer in nanostructures even in the case of hetero-structures. This model only requires introducing a new intrinsic thermal parameter called ballistic thermal conductance and a geometric one called the effective thermal conductivity. Finally, this model is able to reproduce accurately advanced numerical results of Monte Carlo simulation for phonons in all phonon transport regime: diffusive (as the Fourier heat transport regime is included), ballistic, and intermediate ones even if thermal interface are involved. This formalism should provide new insights in the interpretation of experimental measurements.