Bias-driven local density of states alterations and transport in ballistic molecular devices

TL;DR

This paper investigates how dynamic nonequilibrium electron charging affects the local density of states and transport properties in ballistic molecular devices, revealing a bias-dependent electronic structure change that influences conductance.

Contribution

It introduces a self-consistent quantum transport approach to study bias-induced local density of states alterations in molecular devices, distinct from static potential barrier effects.

Findings

Local density of states tracks contact electrochemical potentials.

Bias-induced changes alter molecular electronic structure without scattering effects.

Semiconducting molecules show increased resistance due to these effects.

Abstract

We study dynamic nonequilibrium electron charging phenomena in ballistic molecular devices at room temperature that compromise their response to bias and whose nature is evidently distinguishable from static Schottky-type potential barriers. Using various metallic/semiconducting carbon nanotubes and alkane dithiol molecules as active parts of a molecular bridge, we perform self-consistent quantum transport calculations under the nonequilibrium Green's function formalism coupled to a three-dimensional Poisson solver for a mutual description of chemistry and electrostatics. Our results sketch a particular tracking relationship between the device's local density of states and the contact electrochemical potentials that can effectively condition the conduction process by altering the electronic structure of the molecular system. Such change is unassociated to electronic/phononic scattering effects while its extent is highly correlated to the conducting character of the system, giving rise to an increase of the intrinsic resistance of molecules with a semiconducting character and a symmetric mass-center disposition.