Coexistence of antiferromagnetism and dimerization in a disordered spin-Peierls model: exact results

TL;DR

This paper provides exact results for a disordered spin-Peierls model, revealing how disorder influences antiferromagnetism and dimerization, with implications for doped CuGeO3 compounds.

Contribution

It introduces an exactly solvable disordered spin-Peierls model with domain wall disorder, analyzing its thermodynamic behavior and magnetic fluctuations.

Findings

Weak disorder leads to a crossover from pure behavior to singular low-energy regime.

Enhanced antiferromagnetic fluctuations occur at low energies.

Results are relevant for understanding doped CuGeO3.

Abstract

A model of disordered spin-Peierls system is considered, where domain walls are randomly distributed as a telegraph noise. For this realization of the disorder in an XX spin chain, we calculate exactly the density of states as well as several thermodynamic quantities. The resulting physical behavior should be qualitatively unchanged even for an XXZ chain, up to the isotropic XXX point. For weak disorder, besides a high energy regime where the behavior of a pure spin-Peierls system is recovered, there is a cross-over to a low energy regime with singular thermodynamic properties and enhanced antiferromagnetic fluctuations. These regimes are analyzed with the help of exact results, and the relevant energy scales determined. We discuss the possible relevance of such a disorder realization to the doped inorganic spin-Peierls compound CuGeO$_3$.