How Coherence of Thermal Phonons impacts Heat Transport

Physics describes reality as excitations emerging from a collection of coupled oscillators and a typical example of this process is the apparition of thermal phonons. It will be explained how a thermally activated phonon mode involves a large population of elastic wavepackets. These excitations are characterized by a wide distribution of lifetimes and coherence times expressing particle- and wave-like natures. In agreement with direct simulations, our theoretical derivation yields a generalized law for the decay of the phonon number taking into account coherent effects. Several examples of applications of this law will be presented. This work opens new horizons in the understanding of the origin and the treatment of thermal phonons.