Real-space subfemtosecond imaging of quantum electronic coherences in molecules

Tracking electron motion in molecules is the key to understanding and controlling chemical transformations. Contemporary techniques in attosecond science are able to generate and trace the consequences of this motion in real time, but not in real space. Scanning tunnelling microscopy, on the other hand, can locally probe the valence electron density in molecules, but cannot alone provide dynamical information at this ultrafast timescale. Here we show that, by combining scanning tunnelling microscopy and attosecond technologies, quantum electronic coherences induced in molecules by <6-fs-long carrier-envelope-phase-stable near-infrared laser pulses can be directly visualized at ångström-scale spatial and subfemtosecond temporal resolutions. We demonstrate concurrent real-space and -time imaging of coherences involving the valence orbitals of perylenetetracarboxylic dianhydride molecules, and full control over the population of the involved orbitals. This approach opens the way to the unambiguous observation and manipulation of electron dynamics in complex molecular systems.