Boundary condition for phonon distribution functions at a smooth crystal interface and interfacial angular momentum transfer
The research develops boundary conditions for phonon distribution functions at smooth crystal interfaces, bridging classical lattice vibrations and quantum mechanics. It first establishes a model for thermal transport (Kapitza resistance) using acoustic mismatch principles. Subsequently, it refines these conditions to show that circularly polarized phonons generate orbital angular momentum (OAM) at the interface, demonstrating the coupling between spin and orbital angular momentum in phonon diffusion.