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

Area of Science:

• Molecular electronics
• Plasmonics
• Quantum transport

Background:

• Understanding electron transport in molecular junctions is crucial for nanoscale electronic devices.
• Light-induced phenomena offer novel ways to control charge transport at the molecular level.

Purpose of the Study:

• To investigate the light-induced plasmon-mediated electron transport characteristics of a molecular-scale junction.
• To elucidate the underlying mechanisms responsible for the observed nonlinear current response.

Main Methods:

• Combined experimental, theoretical, and first-principles-based calculations.
• Utilized a chopped laser beam to perturb the tip-sample junction.
• Applied a theory of electronic nonequilibrium and decoherence of optically triggered plasmons.
• Performed first-principles transport calculations.

Main Results:

• Experimental data revealed a nonlinear increase in electronic current perturbation as the laser focus approached the junction.
• The theoretical model demonstrated that current increases nonlinearly with increasing energy.
• Higher injection energies lead to increased availability of virtual molecular orbital channels for transport.

Conclusions:

• Light can trigger and enhance tunneling current in molecular junctions via plasmon mediation.
• The nonlinear current response is attributed to the energy-dependent availability of molecular orbital transport channels.
• This study provides fundamental insights into light-matter interactions in molecular electronic systems.