Phonon interference effects in GaAs-GaP superlattice nanowires

Abstract: Fine-tuning the functional properties of nanomaterials is crucial for technological applications. Superlattices, characterized by periodic repetitions of two or more materials in different dimensions, have emerged as a promising area of investigation. We present a study of the phonon interference effect on thermal transport in GaAs-GaP superlattice nanowires with sharp interfaces between the GaAs and GaP layers, as confirmed by high-resolution transmission electron microscopy. We performed thermal conductivity measurements using the so-called thermal bridge method on superlattice nanowires with a period varying from 4.8 to 23.3 nm. The measurements showed a minimum of the thermal conductivity as a function of superlattice period up to room temperature, that we interpreted as an indication of the crossover from coherent to incoherent thermal transport. Notably, this effect is not destroyed by surface boundary or by phonon-phonon scattering, as the crossover trend is also observed at room temperature. Our results were corroborated by both ab initio lattice dynamics and semiclassical nonequilibrium molecular dynamics calculations. These findings provide insights into the wave-like and particle-like transport of phonons in superlattice nanowires and demonstrate the potential for engineering thermal properties through precise control of the superlattice structure.