Theory of vibrationally inelastic electron transport through molecular bridges

Abstract

Vibrationally inelastic electron transport through a molecular bridge that is connected to two leads is investigated. The study is based on a generic model of vibrational excitation in resonant transmission of electrons through a molecular junction. Employing methods from electron-molecule scattering theory, the transmittance through the molecular bridge can be evaluated numerically exactly. The current through the junction is obtained approximately using a Landauer-type formula. Considering different parameter regimes, which include both the case of a molecular bridge that is weakly coupled to the leads, resulting in narrow resonance structures, and the opposite case of a broad resonance caused by strong interaction with the leads, we investigate the characteristic effects of coherent and dissipative vibrational motion on the electron transport. Furthermore, the validity of widely used approximations such as the wideband approximation and the restriction to elastic transport mechanisms is investigated in some detail.

Suppression of electron–vibron coupling in graphene nanoribbons contacted via a single atom

“…As the lifetime is shortened, the vibronic features decrease in intensity 29 , in line with our results. In addition, formation of an atomic contact increases dissipation, leading to a faster decay of the vibrationally excited state and to a decrease of inelastic carrier transport 34 .…”

The influence of ultrafast laser pulses on electron transfer in molecular wires studied by a non-Markovian density-matrix approach

“…In this aspect these approaches are very similar to Redfield-like approaches in the field of dissipative quantum dynamics. Furthermore, in some theories the wire is coupled to a dissipative environment to mimic relaxation and decoherence in the wire 21,22,23,24 or to determine current-induced light emission 25 . Additional effects are observed when the molecular wire is irradiated by a periodic laser field 17,24,26,27 .…”

Coherent charge transport through molecular wires: Influence of strong Coulomb repulsion

“…The treatment of these models can be distinguished according to the level at which interaction is taken into account. Here, we are in particular interested in two situations in which the many-body problem can be traced back to the dynamics of single electrons on the wire: The first case premises non-interacting electrons for which the current can be computed from a Landauer-like formula [15][16][17][18][19][20]. The second case deals with the opposite limit in which Coulomb repulsion is so strong that at most one excess electron can be located on the molecule.…”