Stability of moving solitons in trans-polyacetylene in an electric field

TL;DR

This paper investigates the stability and dynamics of charged solitons in trans-polyacetylene under an external electric field using the SSH model, identifying instability mechanisms and proposing a stability measure.

Contribution

It introduces a new quantitative measure for soliton stability and analyzes the microscopic mechanisms of dynamical instabilities under electric fields.

Findings

Identified the microscopic mechanisms triggering soliton instabilities.

Proposed a quantitative measure for soliton stability.

Analyzed soliton dynamics in low electric fields using the SSH model.

Abstract

In this work we study the dynamics and stability of charged solitons in trans-polyacetylene (tPA), and revisit the issue of the stability of these non-linear excitations under the effect of an external electric field applied parallel to the polymer. Using the formalism of the Su-Schrieffer-Heeger (SSH) model, we solve the coupled dynamical equations for electrons and classical nuclei at the mean-field level and in the regime of low external electric field $E$, where the dynamics of the moving soliton is adiabatic. Analyzing observable quantities in real space and frequency space, we identify the microscopic mechanisms triggering the dynamical instabilities of the soliton. In addition, we put forward the definition of a proper quantitative measure of its stability, an issue which to the best of our knowledge has remained an open question. Besides its intrinsic interest from the fundamental point of view, our work might be relevant for the design of novel organic electronic devices based on soliton-mediated transport.