Chiral Phonon-Induced Spin Transport via Microscopic Barnett Effect.

Chiral phonons, which are characterized by rotational atomic motion, offer a unique mechanism for transferring angular momentum from phonons to electron spins and other angular momentum carriers. In this Letter, we present a theoretical investigation into the emergence of chiral phonons in a chiral hybrid organic-inorganic perovskite (HOIP) and their critical roles in rigid-body rotation, magnetic moment generation, and spin transport under nonthermal equilibrium conditions. We demonstrate that phonon angular momentum can modify the spin chemical potential via a proposed microscopic Barnett effect, leading to a spatially varying spin chemical potential at the metal/HOIP interface, which subsequently induces spin currents in an adjacent Cu layer, with a magnitude consistent with experimental observations. Additionally, we propose a mechanism for the intrinsic excitation of spin currents driven by chiral phonons under a parabolic temperature profile. Beyond their influence on spin transport, we also outline experimental approaches to probe chiral phonons through their distinctive mechanical and magnetic responses.