In a new study published in Nature Physics, scientists have achieved the first experimental observation of phonon angular momentum in chiral crystals.

Phonons are the quantized lattice vibrations representing sound and heat in crystals. Theoretically, phonons have been predicted to carry finite angular momentum with potentially remarkable macroscopic consequences.

The famous Einstein-de Haas effect explains how quantum mechanical spin connects to classical angular momentum when a ferromagnetic cylinder rotates under magnetic fields. While this effect has been known for over a century, the phonon version had remained purely theoretical until now.