Enhanced magnetic fluctuations in doped spin-Peierls systems: a single-chain model analysis

TL;DR

This paper investigates how doping affects magnetic fluctuations in a spin-Peierls system using a single-chain model, revealing enhanced magnetic correlations due to disorder within a specific temperature range.

Contribution

It provides an analytical and numerical analysis of a doped spin-Peierls chain, highlighting the role of localized moments and disorder in magnetic fluctuation enhancement.

Findings

Magnetic correlations are enhanced by disorder below the spin-Peierls transition.

A crossover temperature range is identified where these effects are prominent.

Results are relevant to understanding doped CuGeO$_3$ behavior.

Abstract

We analyze by means of real space Renormalization Group (RG) as well as by exact diagonalizations the properties of a single-chain model of a doped spin-Peierls system, where a major role is played by the localized moments created by the impurities. We are able to follow analytically the RG flow, which allows us to determine the relevant cross-over temperatures. In particular, we find an enhancement of magnetic correlations due to disorder, coexisting with an underlying dimerization, in an intermediate temperature range below the spin-Peierls critical temperature and above the coherence temperature of a regular array built by those localized moments (so-called soliton bandwidth). The possible relevance of these results to the doped inorganic spin-Peierls compound CuGeO$_3$ is discussed.