Energetics and dynamics of laser-assisted field emission from silicene nanoribbons: Time-dependent first-principles study

Abstract

We investigate laser-assisted field emission (LAFE) from a silicene nanoribbon (SiNR) using time-dependent density functional theory (TDDFT) simulation. The emission mechanism in the present study is considered to be over-barrier photoemission and is found to be governed by electronic dipole transitions, the characteristics of the excited states, and the energy levels of the excited states relative to the potential hump. The qualitative features of emission from the SiNR are similar to those from graphene nanoribbons (GNRs). The emission currents from SiNR, however, are found to be much larger than those from GNR for the same laser parameters in spite of a larger work function for SiNR. We reveal the emission currents in real time and space on an atomic scale, and observed current being driven back and forth in the early stage of emission. We further elucidate the dynamical correlation among the laser pulse, the Kohn-Sham potential and emission currents wiggling under the ponderomotive force.