A new Nature Physics Perspective co-authored by Dr Habib Rostami clarifies what should count as a chiral phonon and introduces a simple taxonomy for phonons with angular momentum. The authors reserve “chiral phonon” for vibrations that break improper rotational symmetry, and use “axial phonon” for modes that carry real and/or pseudo angular momentum. This framework ties together recent results on phonon magnetic moments and Zeeman splittings, thermal Hall and related transport, and ultrafast Einstein–de Haas/Barnett effects, and it specifies when circularly polarized modes in 2D and 3D are truly chiral, false chiral, or merely axial.

This Perspective offers a practical roadmap for controlling heat, spin, and light with lattice vibrations (phonons), and highlights open problems linking chirality, angular momentum (real vs pseudo), and topology—pointing to opportunities in phonomagnetism, chiral transport, and light-induced chirality.

Reference:

Dominik M. Juraschek, R. Matthias Geilhufe, Hanyu Zhu, Martina Basini, Peter Baum, Andrey Baydin, Swati Chaudhary, Michael Fechner, Benedetta Flebus, Gael Grissonnanche, Andrei I. Kirilyuk, Mikhail Lemeshko, Sebastian F. Maehrlein, Maxime Mignolet, Shuichi Murakami, Qian Niu, Ulrich Nowak, Carl P. Romao, Habib Rostami, Takuya Satoh, Nicola A. Spaldin, Hiroki Ueda & Lifa Zhang
“Chiral phonons.”
Nature Physics (2025)