Applied Physics Letters, Год журнала: 2025, Номер 126(14)

Опубликована: Апрель 1, 2025

Silicon carbide (SiC) crystallizes in more than 200 polytypes with various crystal classes, including cubic, hexagonal, and rhombohedral structures. They differ from each other mainly by the stacking order of hexagonal SiC atomic layers. Such superlattice-like modulates phonon dispersion folding single SiC-layer Brillouin zone into smaller ones along axial direction normal to layer, resulting an increased number branches. Earlier works suggest that these share a common unfolded direction. We show first principles this is only true for high-symmetry line. For general k points such as planar path, strong hybridization between longitudinal transverse phonons large avoided crossings are observed. The difference direct consequence distinctive symmetry decrease explained group theory. crossing soften velocity enhance scattering folded acoustic phonons, leading significant thermal conductivity reduction complex polytypes, confirmed Boltzmann transport calculations phonon–phonon principles. This work provides unified description comparison on equal footing physical perspectives impact behaviors.

Язык: Английский