Vibrations of atoms in a crystal of the semiconductor gallium arsenide (GaAs) are impulsively shifted to a higher frequency by an optically excited electric current. The related change in the spatial distribution of charge between gallium and arsenic atoms acts back on their motions via electric interactions.
![](https://scx1.b-cdn.net/csz/news/tmb/2020/hammerontech.jpg)
Source:
https://phys.org/news/2020-07-hammer-on-technique-atomic-vibrations-crystal.html