Crucial role of decoherence for electronic transport in molecular wires: Polyaniline as a case study

TL;DR

This paper demonstrates that decoherence plays a crucial role in enabling high electronic conductance in disordered polyaniline, challenging the traditional view that coherence is necessary for conductivity in such polymers.

Contribution

It shows that decoherence can explain high conductance in disordered bipolaronic lattices of polyaniline without invoking a mixed model of conducting islands and insulating strands.

Findings

Decoherence enables conduction in disordered bipolaronic lattices.

Without dephasing, short bipolaronic strands cannot sustain transport.

Decoherence mechanisms relate to Marcus-Hush electron transfer theory.

Abstract

In this work we attempt to elucidate the nature of conductivity in polymers by taking the acid-base doped polyaniline (PAni) polymer. We evaluate the PAni conductance by using realistic ab initio parameters and including decoherent processes within the minimal parametrization model of D'Amato-Pastawski. In contrast to general wisdom, which associates the conducting state with coherent propagation in a periodic polaronic lattice, we show that decoherence can account for high conductance in the strongly disordered bipolaronic lattice. Hence, according to our results, there is no need of considering a mix model of "conducting" polaronic lattice islands separated by "insulating" bipolaronic lattice strands as is usually assumed for PAni. We find that without dephasing events, even very short strands of bipolaronic lattices are not able to sustain electronic transport. We also include a discussion of specific mechanisms that should be involved in decoherence rates of PAni and relate them with Marcus-Hush theory of electron transfer.