Carrier-envelope phase effects on the strong-field photoemission of electrons from metallic nanostructures

Sharp metallic nanotapers irradiated with few-cycle laser pulses are emerging as a source of highly confined coherent electron wave packets with attosecond duration and strong directivity(1-6). The possibility to steer, control or switch such electron wave packets with light(7) is expected to pave the way towards direct visualization of nanoplasmonic field dynamics(8-10) and real-time probing of electron motion(11,12) in solid-state nanostructures(13,14). Such pulses can be generated by strong-field-induced tunnelling and acceleration of electrons in the near-field of sharp gold tapers within one half-cycle of the driving laser field(1,2,5). Here, we show the effect of the carrier-envelope phase of the laser field on the generation and motion of strong-field-emitted electrons from such tips. We observe clear variations in the width of plateau-like photoelectron spectra characteristic of the subcycle regime. This is a step towards controlling the coherent electron motion in and around metallic nanostructures over ultrashort lengths and timescales.