Dynamical symmetry breaking in vibration-assisted transport through nanostructures

TL;DR

This paper presents a theoretical model of electron transport through a molecule with multiple vibronic modes, revealing phenomena like gate asymmetry and negative differential conductance due to strong electron-vibron interactions.

Contribution

It introduces a fully symmetric model considering multiple vibronic modes with degenerate configurations, highlighting novel transport features arising from strong coupling.

Findings

Gate asymmetry observed in transport characteristics

Pronounced negative differential conductance features

Slow channels caused by Franck-Condon suppression and degeneracies

Abstract

A theoretical model of a single molecule coupled to many vibronic modes is presented. At low energies, transport is dominated by electron-vibron processes where transfer of an electron through the dot is accompanied by the excitation/emission of quanta (vibrons). Because the frequency of the $n$th mode is taken as an $n$th multiple of the frequency of the fundamental mode, several energetically degenerate or quasi-degenerate vibronic configurations can contribute to transport. We investigate the consequences of strong electron-vibron coupling in a fully \emph{symmetric} set-up. Several striking features are predicted. In particular, a gate-asymmetry and pronounced negative differential conductance features are observed. We attribute these features to the presence of slow channels originating from the interplay of Franck-Condon suppression of transport channels and spin/orbital degeneracies.