Strong-field effects and attosecond control of electrons in photoemission from a nanoscale metal tip

We focus few-cycle Titanium:sapphire oscillator pulses on a sharp tungsten tip and measure spectra of the emitted electrons. We observe abovethreshold photoemission with a photon order of up to nine, peak shifting and peak suppression, and carrier-envelope phase sensitive photoemission. In a first attempt to understand the underlying physics we model the behavior with theory models borrowed from atomic physics, namely the Three-Step Model and an integration of the one-dimensional time-dependent Schr̈odinger equation. The models match the high-energy part of the spectra surprisingly well, and we infer that re-scattering and much of the well-known underlying physics of the Three-Step Model takes also place here, even though the parameters are such that this is almost surprising; for instance, the classical excursion of the electrons is only slightly larger than one atomic diameter.