Direct observation of phonon Anderson localization in Si/Ge aperiodic superlattices

Phonon Anderson localization has been receiving increasing interest in creating unique thermal transport properties. However, due to challenges to resolve and track the mode-specific transmission, the existence of phonon Anderson localization has only been inferred from the decay of overall thermal conductivity versus device length. In this work, we present direct evidence of phonon Anderson localization using the exponential decay of their mode-resolved transmissions. We clearly capture localized modes in different structures, even with a monotonically upward thermal conductivity trend.