Disorder-induced neutral solitons in degenerate ground state polymers

TL;DR

This paper investigates how weak off-diagonal disorder in degenerate ground state polymers induces neutral solitons, affecting magnetic properties and revealing potential experimental signatures in trans-polyacetylene.

Contribution

It demonstrates that disorder creates neutral solitons in polymers and explores how interchain interactions influence their density and magnetic behavior.

Findings

Disorder induces a finite density of neutral solitons.

Interchain interactions can bind solitons into pairs, suppressing their density.

Neutral solitons contribute to the magnetic susceptibility of the polymer.

Abstract

In this letter, we study the effects of weak off-diagonal disorder on conjugated polymers with a doubly degenerate ground-state. We find that disorder induces a finite density of neutral solitons in the lattice dimerization of a polymer chain. Interchain interactions result in a linear potential between the solitons and, if sufficiently strong, bind them into pairs resulting in an exponential suppression of the soliton density. As neutral solitons carry spin 1/2, they contribute to the polymer's magnetic properties. We calculate the magnetic susceptibility and suggest measurements of the magnetic susceptibility in {\it trans}-polyacetylene at low temperatures.