All-optical microscopy with combined atomic-scale spatial and subcycle temporal resolution

In condensed matter physics, there has been a long-standing effort to probe light-matter interaction at the shortest possible length and time scales. Scanning near-field optical microscopy (SNOM), which relies on evanescent fields confined to nanoscale metallic structures, provides valuable insights into these interactions but is fundamentally limited in spatial resolution by the probe apex size (~10 nm) [1]. On the other hand, lightwave-driven scanning tunnelling microscopy (LW-STM) has revealed atomic-scale dynamics [2,3]. However, it is unable to resolve the ultrafast motion of electrons within a single optical cycle, capturing only the time-averaged electronic response in the form of rectified currents. Here, we present a new optical microscopy approach that exploits strong-field nonlinearities to achieve atomic-scale spatial resolution combined with subcycle temporal precision [4].