Sub-optical-cycle electron pulse trains from metal nanotips

Abstract The coherent modulation of swift electron beams with strong laser fields has enabled the generation attosecond pulses, opening up new research avenues in ultrafast science. Here we study a comparatively simple alternative, production pulse trains directly at source. In our theory work, show that sub-optical-cycle bursts induced by tunneling photoemission from metal nanotip can retain temporal fingerprint their emission dynamics typical low-energy point-projection microscope setup. We find acceleration static field, short propagation distance and sufficiently large optical cycle duration mitigate smearing due to matter-wave dispersion. Our approach enables studies interactions slow electrons matter on sub-femtosecond nanometer scales, regime which hitherto remained inaccessible.