Super-resolution in time and space: exploring the nano-world faster than a cycle of light

Scanning probe microscopies such as atomic force microscopy and scanning tunneling microscopy provide access to the details of material surfaces with unsurpassed spatial resolution. By coupling light to these probes, one can even image optical properties in nanostructures far smaller than the free space wavelength. The low energy elementary excitations in such nanomaterials—such as plasmons, phonons, and interlevel transitions in excitons—are of particular importance for nanomaterial functionality, as are their ultrafast dynamics. These processes typically survive for only femtoseconds to picoseconds after photoexcitation and can evolve within a single oscillation period. Techniques capable of simultaneous sub-cycle time resolution and nanometer spatial resolution are therefore necessary to capture their full detail and record ultrafast nano-movies. In this talk, I will present two novel approaches for resolving far- and mid-infrared excitations on the nanoscale with time resolution faster than a single oscillation cycle of light: field-resolved multi-terahertz near-field nanoscopy and terahertz scanning tunneling microscopy.