Spin-wave theory for dimerized ferromagnetic chains

TL;DR

This paper introduces a modified spin-wave theory to describe finite-temperature dimerization in ferromagnetic chains, achieving results that align well with numerical methods and analyzing thermodynamic properties.

Contribution

It presents a novel modification to spin-wave theory using a Lagrange multiplier to accurately model finite-temperature dimerization in ferromagnetic chains.

Findings

Excellent agreement with density-matrix renormalization group results

Identification of characteristic features of dimerization in specific heat

Analysis of bond correlation functions

Abstract

We describe a Peierls dimerization which occurs in ferromagnetic spin chains at finite temperature, within the modified spin-wave theory. Usual spin-wave theory is modified by introducing a Lagrange multiplier which enforces a nonmagnetic state at finite temperature. It is shown that this method gives results in excellent agreement with the density--matrix renormalization group applied to transfer matrices for dimerized ferromagnetic chains. We study bond correlation functions and explore the characteristic features of dimerization in the specific heat.