Vibrationally Induced Decoherence in Single-Molecule Junctions

TL;DR

This paper explores how vibrational effects cause decoherence in electron transport through single-molecule junctions, revealing that inelastic processes diminish quantum interference and significantly affect transport properties.

Contribution

It introduces a nonequilibrium Green's function approach to analyze vibrationally induced decoherence and its impact on quantum interference in molecular electronics.

Findings

Vibrational inelastic processes quench quantum interference effects.

Bias voltage and vibrational excitation increase decoherence.

Vibrational signatures deviate from simple Franck-Condon models.

Abstract

We investigate the interplay of quantum interference effects and electronic-vibrational coupling in electron transport through single-molecule junctions, employing a nonequilibrium Green's function approach. Our findings show that inelastic processes lead, in general, to a quenching of quantum interference effects. This quenching is more pronounced for increasing bias voltages and levels of vibrational excitation. As a result of this vibrationally induced decoherence, vibrational signatures in the transport characteristics of a molecular contact may strongly deviate from a simple Franck-Condon picture. This includes signatures in both the resonant and the non-resonant transport regime. Moreover, it is shown that local cooling by electron-hole pair creation processes can influence the transport characteristics profoundly, giving rise to a significant temperature dependence of the electrical current.