Complex-band structure: a method to determine the off-resonant electron transport in oligomers

TL;DR

This paper introduces a method to analyze off-resonant electron transport in ultra-short oligomer molecular junctions by using complex-band structure to determine conductance decay, validated through first-principles calculations.

Contribution

It presents a novel approach linking complex-band structure to off-resonant conductance decay in molecular junctions, validated with first-principles calculations.

Findings

Conductance decays exponentially with length in ultra-short oligomers.

Complex-band structure accurately predicts conductance damping.

First-principles calculations confirm the method's validity.

Abstract

We validate that off-resonant electron transport across {\it ultra-short} oligomer molecular junctions is characterised by a conductance which decays exponentially with length, and we discuss a method to determine the damping factor via the energy spectrum of a periodic structure as a function of complex wavevector. An exact mapping to the complex wavevector is demonstrated by first-principle-based calculations of: a) the conductance of molecular junctions of phenyl-ethynylene wires covalently bonded to graphitic ribbons as a function of the bridge length, and b) the complex-band structure of poly-phenyl-ethynylene.