A microscopic approach to the dimerization in the frustrated spin-1/2 antiferromagnetic chains

TL;DR

This paper investigates the spontaneous dimerization in frustrated spin-1/2 antiferromagnetic chains using a microscopic approach with composite operators, employing spin-wave and coupled-cluster methods to analyze ground states and excitations.

Contribution

It introduces a systematic microscopic framework combining spin-wave and coupled-cluster methods to study dimerization in frustrated chains, highlighting the advantages of CCM for improvements.

Findings

Ground-state properties depend on coupling parameters

Triplet excitation spectra are characterized

Comparison shows CCM's systematic improvement capability

Abstract

The spontaneous dimerization of the frustrated spin-$1\over2$ antiferromagnetic chains is studied by a microscopic approach based on a proper set of composite operators (i.e., pseudo-spin operators). Two approximation schemes are developed. Firstly, a spin-wave approximation is made by a Dyson-Mal\'eev-like boson transformation. The ground-state properties and the triplet excitation spectra are obtained as functions of the coupling parameter. Secondly, based on the pseudo-spin operators, a microscopic treatment is formulated within the framework of the powerful, systematic coupled-cluster method (CCM). Comparison between various approximations is made. The advantage of the CCM for the purposes of systematic improvement is emphasized.