Quenching Strong-Field Rescattering of Photoemitted Electrons from Metallic Nanotapers by Using Moderate Bias Fields

The rescattering of photoemitted electrons with the ionized emitter is a central process in strong-field photoemission from atomic, molecular, and solid-state systems, resulting in characteristic rescattering plateaus in the photoelectron spectra. Recently, the appearance of such plateaus was also observed in the multiphoton photoemission regime from metallic nanostructures, raising questions about their effects on the dynamics of the photoemission process. Here, we analyze the effects of external static electric fields on electron rescattering from tungsten nanotapers illuminated by intense, few-cycle near-infrared laser pulses. In the strong-field regime, we observe distinct changes in the spectral shape of the plateau region. Time-dependent Schrödinger equation simulations of the photoemission dynamics show that this spectral reshaping is a signature of the suppression of recollisions at sufficiently high bias voltages. This suppression predicts the generation of low-energy electron pulses with few-femtosecond subcycle duration and emission characteristics that maintain this pulse duration over mesoscopic propagation distances in the 100 nm range. An experiment is proposed to directly probe the time structure of such subcycle electron pulses.