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

We present a novel contrast mechanism in near-field microscopy that enables all-optical atomic-scale imaging with subcycle temporal resolution. This approach hinges upon the idea of performing near-field microscopy under ultrahigh vacuum conditions, at low temperatures, and with sub-nanometer tip tapping amplitudes. At these scales, a remarkably efficient non-classical near-field response emerges, tightly confined to atomic dimensions and governed by the light's vector potential. This ultrafast signal is characterized by an optical phase delay of approximately π/2, allowing precise tracking of tunneling dynamics. Our method uncovers nanoscale defects and captures current transients in semiconducting van der Waals materials with subcycle sampling. This capability enables the real-time recording of the quantum flow of electrons in both conductive and insulating quantum materials, achieving ultimate spatiotemporal resolution.