How Chiral Phonons Work—and Why They Matter

Atoms That Dance in Circles

Inside every solid material, atoms vibrate. These vibrations, quantized into packets called phonons, carry heat and sound through crystal lattices. Most phonons oscillate back and forth in straight lines. But in certain crystals with asymmetric structures, atoms do something far more interesting: they move in tiny circles, spiraling clockwise or counterclockwise like coordinated dancers.

These circular lattice vibrations are called chiral phonons. First observed experimentally in 2018 at Lawrence Berkeley National Laboratory, they have since become one of the most exciting frontiers in condensed matter physics—because their spinning motion carries something valuable: angular momentum.

What Makes a Phonon "Chiral"?

Chirality, from the Greek word for "hand," describes objects that cannot be superimposed on their mirror image. A chiral phonon vibrates in a rotational pattern that has a definite handedness—left or right. This happens when a crystal's lattice structure breaks what physicists call inversion symmetry, meaning the arrangement of atoms looks different when flipped through a central point.

Materials like α-quartz, tellurium, and selenium naturally possess this asymmetry. When energy—typically heat—excites their lattice, atoms begin circling rather than simply bouncing. As these chiral phonons propagate through the material, they carry their rotational momentum with them, effectively threading angular momentum through the crystal like a wave.

From Vibration to Electron Control

The breakthrough that elevated chiral phonons from curiosity to potential technology came when researchers at NC State University and the University of Utah demonstrated that chiral phonons can directly transfer their angular momentum to electrons. Published in Nature Physics, their study showed that in α-quartz—an ordinary, inexpensive crystal—chiral phonons pushed electrons into orbital motion without any external magnets, batteries, or applied voltage.

The team named this phenomenon the orbital Seebeck effect, by analogy with the well-known spin Seebeck effect. By applying a temperature gradient across the quartz, they excited chiral phonons that collectively passed their angular momentum to electrons in thin tungsten and titanium films deposited on the crystal's surface. The resulting flow of orbital angular momentum was detected through the inverse orbital Hall effect.

"We don't need a magnet, don't need a battery, don't need to use voltage—just a material with chiral phonons," the researchers explained.

Why It Opens the Door to Orbitronics

Today's electronics encode information using electric charge. An emerging alternative, spintronics, uses electron spin. But spintronics typically requires expensive magnetic materials and suffers from rapid signal decay. Chiral phonons offer a third path: orbitronics, where information is carried by the orbital motion of electrons.

Orbitronics holds several advantages. Orbital angular momentum can persist longer than spin in many materials, potentially enabling more efficient data transmission. The materials involved—quartz, tellurium, selenium—are abundant and inexpensive compared to the rare-earth magnets spintronics often demands. And because chiral phonons can be excited simply by heat, orbitronic devices could harvest waste thermal energy to process information.

Challenges Ahead

Significant hurdles remain before orbitronics leaves the laboratory. Maintaining chiral phonon coherence at room temperature is difficult; thermal noise can scramble the delicate circular vibrations. Scaling the effect to produce signals strong enough for practical devices requires further materials engineering. Researchers are also cataloguing which of the thousands of known crystals support robust chiral phonons—a 2026 study in Nature Physics published a symmetry-guided catalogue to accelerate this search.

Still, the fundamental proof of concept is compelling. Chiral phonons demonstrate that the simple act of atoms dancing in circles can control electrons in ways that magnets and voltages cannot—pointing toward a future generation of computing hardware that is faster, cheaper, and dramatically more energy-efficient.