Unraveling a New Heat Transport Regime at The Nanoscale.*

The understanding of heat transport in nanoscale semiconductors is of fundamental importance because of its huge technological impact in electronics and renewable energy harvesting and conversion. A particularly interesting question is related to the understanding of how thermal properties of dielectrics, like silicon, change when their size of the order of a few hundred nanometers, which is the characteristic size of state of the art electronic circuits. In this size range heat transport is in a regime in between ballistic and diffusive, which is inaccurately described by either approximation.
In this work, we analyze the current state of the art of heat transport in semiconductor nanostructures. We identify substantial gaps in the theoretical treatment of the quasi-ballistic transport regime, and we propose a new atomistic model to compute the thermal conductivity of nanoscale systems, including both quantum and finite boundaries effects. Our novel approach is implemented in a computational environment, which gives to the powerful framework of anharmonic lattice dynamics, the ability to perform high accuracy predictions for finite size systems, and provide a rigorous alternative to non-equilibrium molecular dynamics.