Ferroelectric materials, which exhibit spontaneous electric polarization that can be reversed, are critical for technologies such as nonvolatile memories and sensors. Bismuth ferrite (, or BFO) is particularly promising because it combines ferroelectricity with light sensitivity, enabling ultrafast, light-controlled applications. However, the atomic-scale mechanisms that underpin BFO’s rapid response to light—especially in the first trillionths of a second after excitation—have remained unclear.
