Magnetic Susceptibility Due to Disorder-Induced Neutral Solitons in Interacting Polymer Chains

TL;DR

This paper investigates how disorder-induced neutral solitons in interacting polymer chains affect magnetic susceptibility, revealing deviations from Curie behavior at low temperatures and providing analytical insights into soliton pairing and magnetic responses.

Contribution

It introduces an analytical model accounting for interchain interactions and soliton pairing, advancing understanding of magnetic susceptibility in disordered polymer systems.

Findings

Magnetic susceptibility deviates from Curie law at low temperatures.

Interchain interactions lead to bound soliton pairs affecting magnetic response.

Model matches experimental data on trans-polyacetylene susceptibility.

Abstract

We study the magnetic response due to neutral solitons induced by disorder in polymer materials. We account for interchain interactions, which, if sufficiently strong, result in a bond-ordered phase, in which the neutral solitons are bound into pairs. We analytically calculate the corresponding pair size distribution. As the spins of the solitons have a distance dependent antiferromagnetic coupling, this allows us to calculate the magnetic susceptibility in the ordered phase. At low temperatures, the result deviates from the usual Curie behavior in a way that depends on the relative strength of the disorder and the interchain interactions. We compare our results to the observed magnetic susceptibility of trans-polyacetylene and we suggest new experiments extending towards lower temperatures.