Quantum Interference and Decoherence in Single-Molecule Junctions: How Vibrations Induce Electrical Current

TL;DR

This paper investigates how vibrational interactions in single-molecule junctions influence quantum interference and electrical current, revealing that vibrations can suppress interference effects and enhance current flow.

Contribution

It introduces a nonequilibrium Green's function approach to analyze vibrationally induced decoherence and interference quenching in molecular electronic transport.

Findings

Vibrations strongly quench quantum interference effects.

Electronic-vibrational coupling can increase electrical current.

Vibrational excitation enhances decoherence in the junction.

Abstract

Quantum interference effects and decoherence mechanisms in single-molecule junctions are analyzed employing a nonequilibrium Green's function approach. Electrons tunneling through quasi-degenerate states of a nanoscale molecular junction exhibit interference effects. We show that electronic-vibrational coupling, inherent to any molecular junction, strongly quenches such interference effects. As a result, the electrical current can be significantly larger than without electronic-vibrational coupling. The analysis reveals that the quenching of quantum interference is particularly pronounced if the junction is vibrationally highly excited, e.g. due to current-induced nonequilibrium effects in the resonant transport regime.