A pentacene molecule is like a tiny top that can spin in two directions. Normally, you need a magnet to flip its direction. But in this work, no magnet was needed: sound did the job instead.

A thin film of pentacene was placed on a lithium niobate plate. A surface acoustic wave was sent across the plate, like ripples on water, but in a solid. The wave mechanically jostled the molecules and changed their spin state. It worked at room temperature, with no external magnetic field.

Spectroscopy revealed that the spin was indeed switching. The scientists observed Rabi oscillations — oscillations between two states, like a pendulum swinging back and forth. The stronger the sound, the faster the "pendulum" swung.

This magnet-free way of controlling spin could be useful in future devices where small size and low power consumption matter. Sound turned out to be just as precise a tool as a magnetic field.