Propagation and Manipulation of Chiral Phonons

Chiral phonons, as an emerging degree of freedom in lattice vibrations, have become a research hotspot in condensed matter physics in recent years. This article systematically reviews the development of chiral phonons from two-dimensional localized modes to three-dimensional propagating modes, focusing on the realization conditions of propagating chiral phonons, the chiral phonon diode effect, the interfacial transmission of topological chiral phonons, as well as the electrical, magnetic, and optical manipulation mechanisms of chiral phonons. Despite significant progress in understanding phonon angular momentum and chirality, several fundamental challenges remain, including the experimental verification of propagating chiral phonons, efficient detection of phonon angular momentum, and the development of scalable approaches for active manipulation. Bridging the gap between theoretical predictions and experimental realization has therefore become a central challenge for advancing chiral phonon-based technologies. By analyzing theoretical studies and computational simulations in various material systems including WN$_2$, Te, $\alpha$-quartz, hexagonal BN, transition metal dichalcogenides, BaTiO$_3$, In$_2$Se$_3$, and BPO$_4$, this article demonstrates the great potential of chiral phonons as information carriers. Propagating chiral phonons enable long-distance transmission of chiral information and angular momentum; the chiral phonon diode effect achieves directional filtering of chirality; topologically protected chiral interface modes provide dissipationless transport channels; and various manipulation means including electric field, magnetic field, and light field open new avenues for active control of chiral phonons. Furthermore, we discuss the limitations of current detection and manipulation strategies, including the difficulty of selectively exciting chiral phonon modes, the requirement of high-quality material platforms, and the challenges in achieving fast, efficient, and device-compatible control. These issues provide important directions for future exploration of chiral phononics in quantum information processing, low-energy information transport, and topological phonon devices. These advances not only deepen our fundamental understanding of phonon angular momentum and chiral coupling but also lay the theoretical foundation for designing novel quantum devices based on chiral phonons.