Electron transport properties of molecular junctions with anharmonic double-well potentials

In the present paper, we investigated the electron transport properties of molecular junctions with anharmonic vibrations described by double-well potentials in the sequential tunneling regime. It was found that the suppression of the low-bias current caused by strong electron-vibration couplings under harmonic approximation, i.e., the Franck-Condon blockade effect, could be lifted in the case of symmetric double-well potentials. The removal of the Franck-Condon blockade effect is a result of the distribution of the ground vibrational wave function in the two wells. Such a feature also enables the Franck-Condon blockade effect to be restored by breaking the symmetry of the double-well potential. We further demonstrated that the special vibrational transition properties of asymmetric double-well potentials could enable the effective modulation of the charge transport properties of such molecular junctions in the Franck-Condon blockade region by inducing population in excited vibrational levels with external fields such as infrared excitation.

Automated summary

In this study, the electron transport properties of molecular junctions with anharmonic vibrations described by double-well potentials were investigated. It was observed that the Franck-Condon blockade effect could be lifted in the case of symmetric double-well potentials, but restored by breaking the symmetry. Additionally, asymmetric double-well potentials could enable effective modulation of charge transport properties in the Franck-Condon blockade region by inducing population in excited vibrational levels with external fields such as infrared excitation.