Phonon chirality tuned through interface transmission in a one-dimensional atomic junction model

There has been growing interest in revealing exotic properties of chiral phonons since they were found in honeycomb AB lattice, and very recently they were experimentally verified in a tungsten diselenide monolayer (2018 Science 359 579). In this work, we manipulate phonon chirality through interface transmission via a one-dimensional atomic junction model by using the scattering boundary method. Due to the difference of phase change between two transverse directions induced by the anisotropy at interface coupling, the phonon polarization can be tuned between circular and linear in the high-frequency range. In a double-junction atomic model with an anisotropic center, we find that the phase change accumulates when the phonon transmits through the interface material thus the phonon can be tuned between different chirality in the medium frequency range. The phase change is found to linearly depend on the width of the interface material, while the transmission coefficient vibrates. To obtain the same value of the transmission coefficients along the two transverse directions and thus to keep the outgoing phonon circularly polarized, we can connect two interface materials with opposite anisotropy, where the phase-change difference for chirality tuning can be adjusted by the difference of widths of the two materials. Therefore, by using the atomic junction model, we find that the phonon chirality can be effectively tuned through interfaces, which is helpful for the manipulation and application of chiral phonons. (paper)