Plasmon-Mediated Electron Transport in Tip-Enhanced Raman Spectroscopic Junctions

We combine experiment, theory, and
first-principles-based calculations
to study the light-induced plasmon-mediated electron transport characteristics
of a molecular-scale junction. The experimental data show a nonlinear
increase in electronic current perturbation when the focus of a chopped
laser beam moves laterally toward the tip–sample junction.
To understand this behavior and generalize it, we apply a combined
theory of the electronic nonequilibrium formed upon decoherence of
an optically triggered plasmon and first-principles transport calculations.
Our model illustrates that the current via an adsorbed molecular monolayer
increases nonlinearly as more energy is pumped into the junction due
to the increasing availability of virtual molecular orbital channels
for transport with higher injection energies. Our results thus illustrate
light-triggered, plasmon-enhanced tunneling current in the presence
of a molecular linker.