Laser pulse induced transient currents in a molecular junction: Effects of plasmon excitations of the leads

The transient response of a molecular junction excited by a single laser pulse or by a sequence of pulses is studied theoretically utilizing a density matrix description. The approach focuses on the sequential transmission regime and accounts for intramolecular vibrations and vibrational relaxation. Besides the optical excitation of the molecule, also the laser pulse action on the leads is considered. It is accounted for by collective plasmon excitations which also couple to the molecular transitions. Transient currents are calculated as well as averaged dc resulting from a huge sequence of laser pulses. While the transient currents give some insight into the dynamics of the junctions, the averaged dc is ready to be measured in the experiment. Different enhancement effects due to resonant lead-plasmon excitations are highlighted. (C) 2015 AIP Publishing LLC.