Phys.org May 8, 2024
By exploiting linear interaction with tip-confined evanescent light fields, near-field microscopy has reached even higher resolution, prompting a vibrant research field by exploring the nanocosm in motion. Yet the finite radius of the nanometre-sized tip apex has prevented access to atomic resolution. Researchers in Germany leveraged extreme atomic nonlinearities within tip-confined evanescent fields to push all-optical microscopy to picometric spatial and femtosecond temporal resolution. They discovered an unprecedented and efficient non-classical near-field response, in phase with the vector potential of light and strictly confined to atomic dimensions. This ultrafast signal was characterized by an optical phase delay and facilitated direct monitoring of tunnelling dynamics. They showed the power of their optical concept by imaging nanometre-sized defects hidden to atomic force microscopy and by subcycle sampling of current transients on a semiconducting van der Waals material. According to the researchers their results facilitated access to quantum light–matter interaction and electronic dynamics at ultimately short spatio-temporal scales in both conductive and insulating quantum materials… read more. TECHNICAL ARTICLE
Picometric decay of the lightwave-driven emission from tunnelling currents. Credit: Nature volume 629, pages329–334 (2024)