Abstract
The control of thermal waves by the phononic crystal exhibits peculiar behaviors different from the particle picture of phonons and thus has attracted increasing interest. However, the wave nature of phonons is only indirectly reflected in most studies via the macroscopic thermal transport coefficient, such as thermal conductivity. In this work, we investigate directly the coherent interference effect in a graphene superlattice structure at the microscopic phonon mode level via wave-packet simulations. The constructive interference and destructive interference between the reflected phonons give rise to valleys and peaks in the transmission coefficient, respectively, leading to the periodic oscillation of the transmission function with the variation of the superlattice period length. More importantly, both total-transmission and total-reflection of individual phonons have been clearly demonstrated. The physical conditions for realizing the phonon interference have been proposed, which are quantitatively in good agreement with independent wave-packet simulations. Our study provides direct evidence for the coherent phonon interference effect, which might be helpful for the regulation of phonon transport based on its wave nature.
Highlights
Similar to the periodic arrangement of atoms in crystals that gives rise to the electronic band structure, it is found that the artificial structures formed by periodically modulated physical properties can be used to control the transmission of various types of waves based on the band structure theory
We investigate directly the coherent nature of the individual phonon mode in the phononic crystal nanostructure based on the atomic level phonon wave-packet simulations
We have studied the phonon interference in the graphene superlattice structure sandwiched between two pristine graphene segments via phonon wave-packet simulations
Summary
Similar to the periodic arrangement of atoms in crystals that gives rise to the electronic band structure, it is found that the artificial structures formed by periodically modulated physical properties can be used to control the transmission of various types of waves based on the band structure theory. Since phonons are the energy carriers of heat, their particle nature has been widely studied in the literature to understand various scattering mechanisms for applications in thermal management and thermoelectrics.. Xie et al. reviewed the recent advances in the study of the coherent phonon transport in periodic nanostructures. Recent studies demonstrated that phononic crystal nanostructures have the potential to control thermal transport by engineering the phonon dispersion. The coherent interference of phonons gives rise to the peculiar behaviors that cannot be explained by the conventional particle scattering picture, such as the increase in thermal conductivity with the increase in interface density or interface number and the phonon localization.. Most of the existing studies only indirectly reflect the wave nature of phonons via the macroscopic thermal transport coefficient, such as thermal conductivity. The total-transmission and total-reflection phenomena for individual phonons have not yet been clearly demonstrated in the phononic crystal nanostructure
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