Chiral phonons are groups of atoms that move in a circular direction when excited by an energy source, such as heat. As the phonons move through a material, they propagate that circular motion, or angular momentum, through the material. The angular momentum serves as the source of spin, and the chirality dictates the direction of the spin, enabling spin control in spintronics.

Chirality, in simple terms, means that a molecule or material cannot be superimposed on its mirror image—think of your left and right hands, for example. A left-handed glove does not fit on your right hand, and vice versa.

In a new study, researchers used an electric field to switch the chirality of phonons within a ferroelectric crystal. The work could lead to the creation of faster and more energy-efficient spintronic devices.