Phonon Spin Selective One-Way Axial Phonon Transport in Chiral Nanohelix

Abstract: Selectively exciting and manipulating phonons at nanoscale becomes more and more important but still remains challenging in modern nano-energy control and information sensing. Here, we show that the phonon spin angular momentum provides an extra degree of freedom to achieve versatile manipulation of axial phonons in nanomaterials via coupling to spinful multi-physical fields, such as circularly polarized infrared absorption. In particular, we demonstrate the nanoscale one-way axial phonon excitation and routing in chiral nanomaterials, by converting the photon spin in circularly polarized optical fields into the collective interference phonon spin. As exemplified in the smallest chiral carbon nanotube, we show that the rectification rate can reach nearly 100\%, achieving an ideal one-way phonon router, which is verified by molecular dynamics simulations. Our results shed new light on the flexible phonon manipulation via phonon spin degree of freedom, paving the way for future spin phononics.