Density of Neutral Solitons in Weakly Disordered Peierls Chains

TL;DR

This paper investigates how weak off-diagonal disorder in Peierls chains leads to a finite density of neutral, spin-1/2 solitons, affecting the material's optical and magnetic properties.

Contribution

It provides an analytical calculation of disorder-induced soliton density in Peierls systems and compares it with numerical results, highlighting the impact of disorder on soliton formation.

Findings

Disorder induces a finite density of neutral solitons.

Analytical and numerical results agree on soliton density.

Implications for optical and magnetic properties of conjugated polymers.

Abstract

We study the effects of weak off-diagonal disorder on Peierls systems with a doubly degenerate ground state. We show that for these systems disorder in the electron hopping amplitudes induces a finite density of solitons in the minimal-energy lattice configuration of a single chain. These disorder-induced dimerization kinks are neutral and have spin 1/2. Using a continuum model for the Peierls chain and treating the lattice classically, we analytically calculate the average free energy and density of kinks. We compare these results to numerical calculations for a discrete model and discuss the implications of the kinks for the optical and magnetic properties of the conjugated polymer trans-polyacetylene.