Active control of ultrafast electron dynamics in plasmonic gaps using an applied bias

In this joint experimental and theoretical study we demonstrate coherent control of the optical field emission
and electron transport in plasmonic gaps subjected to intense single-cycle laser pulses. Our results show that an
external THz field or a minor dc bias, orders of magnitude smaller than the optical bias owing to the laser field,
allows one to modulate and direct the electron photocurrents in the gap of a connected nanoantenna operating as
an ultrafast nanoscale vacuum diode for lightwave electronics. Using time-dependent density functional theory
calculations we elucidate the main physical mechanisms behind the observed effects and show that an applied
dc field significantly modifies the optical field emission and quiver motion of photoemitted electrons within the
gap. The quantum many-body theory reproduces the measured net electron transport in the experimental device,
which allows us to establish a paradigm for controlling nanocircuits at petahertz frequencies