Microwave emulations and tight-binding calculations of transport in polyacetylene

TL;DR

This paper introduces microwave emulation and tight-binding calculations to study electron transport in polyacetylene chains, revealing the impact of double bonds and edge effects on the transport band gap.

Contribution

It presents a novel combined experimental and theoretical approach to analyze transport properties in polyacetylene, emphasizing the importance of third nearest neighbor couplings.

Findings

Transport band gap appears in long chains with double bonds.

Edge atoms cause resonance peaks within the band gap.

Including third nearest neighbor couplings is essential for accurate modeling.

Abstract

A novel approach to investigate the electron transport of cis- and trans-polyacetylene chains in the single-electron approximation is presented by using microwave emulation measurements and tight-binding calculations. In the emulation we take into account the different electronic couplings due to the double bonds leading to coupled dimer chains. The relative coupling constants are adjusted by DFT calculations. For sufficiently long chains a transport band gap is observed if the double bonds are present, whereas for identical couplings no band gap opens. The band gap can be observed also in relatively short chains, if additional edge atoms are absent, which cause strong resonance peaks within the band gap. The experimental results are in agreement with our tight-binding calculations using the nonequilibrium Green's function method. The tight-binding calculations show that it is crucial to include third nearest neighbor couplings to obtain the gap in the cis-polyacetylene.