Evolution of Phonon Spectral Energy Density in Superlattice Structures

Superlattices are a distinctive class of artificial nanostructures formed by the periodic stacking of two or more materials. The high density of interfaces in these structures often gives rise to exotic physical properties. In the context of thermal transport, it is well established that such interfaces can significantly scatter particle-like phonons while also inducing constructive or destructive interference in wave-like phonons, depending on the relationship between the phonons’ coherence lengths and the superlattice’s period thickness. In this work, we systematically investigate the effect of temperature on the spectral energy density of phonon modes in superlattices. Additionally, we examine how variations in superlattice period thickness influence phonon lifetimes and energy density. Our findings provide critical insights into the spectral phonon properties of superlattices, particularly in terms of their coherence and lifetimes.