Enhanced THz-near-field controls nanotip photoemission

Locally enhanced few-cycle terahertz transients at a sharp metal nanostructure enable a new scheme for ultrafast photoemission control and near-field characterization. We present nanoscale streaking based on electron dynamics in sub-wavelength confined driving fields at nanostructures that are governed by the momentary THz-field at the instance of photoemission. The locally enhanced THz-field allows for a strong enhancement or suppression of the near-infrared photoemission yield. Moreover, time-resolved streaking spectra reveal ultrafast carrier dynamics in and near nanostructures. The presented approach carries potential for electron pulse compression in ultrafast electron diffraction and microscopy experiments.