Strong-field photoemitted electrons from metallic tips show carrier-envelope phase effects

Sharp nanometer-sized metallic tips recently emerged as a test bed for exploring strong-field phenomena such as high-harmonic generation and photoemission [1-4]. When being illuminated with few-cycle laser pulses of sufficient field strength, optical field enhancement at the tip apex results in tunnelling of electrons out of the tip. The acceleration of these electrons within the local near-field gradient can be so strong that the typical quiver motion of the electrons in an oscillating laser field is fully suppressed [3,4]. These sub-cycle electrons traverse the near field with a decay length of only a few nm within less than one half cycle of the laser field. Hence their motion is expected to sensitively depend on the carrier-envelope phase (CEP) of few-cycle driving pulses, enabling steering and controlling of electron motion around metallic nanoparticles by CEP variation.