Revisiting thermal conductivity and interface conductance at the nanoscale

A simple and easy-to-handle semi-analytical model able to describe heat transport in heterostructures of length varying from the nano to the microscale is presented. It consists in redefining three intrinsic parameters: the ballistic thermal conductance, the effective thermal conductivity, and the interface thermal conductance by using two temperatures T+ and T− distinguishing the phonon populations according to the direction of their velocities instead of the standard pseudo-temperature T. The resulting model agrees well with the thermal conductance and temperature profiles predicted by advanced Monte Carlo simulation in all phonon transport regimes, i.e. diffusive, ballistic, and quasi-ballistic regimes, even in the presence of multiple interfaces. It is able to provide new insights into the interpretation of thermal properties of complex nanostructures.