Fractional S^z excitation and its bound state for the S=1/2 antiferromagnetic zigzag spin chain in a magnetic field

TL;DR

This paper investigates fractional S^z excitations and their bound states in a frustrated S=1/2 zigzag antiferromagnetic chain under a magnetic field, elucidating their role in low-energy physics and magnetization features.

Contribution

It reveals the significance of domain-wall excitations with fractional magnetization in explaining the 1/3 magnetization plateau and related phenomena in the zigzag spin chain.

Findings

Fractional S^z=±1/3 excitations describe low-energy physics.

Bound states of these excitations influence magnetization curves.

Explanation of the 1/3 plateau and cusp singularities.

Abstract

We demonstrate that domain-wall type excitations carrying the fractional magnetization $S^z=\pm1/3$ and their bound state describe the low-energy physics around the 1/3 plateau of the antiferromagnetic zigzag spin chain in the strongly frustrated region. In particular we discuss the relevance of such domain-wall excitations to the characteristic properties of the magnetization curves: the 1/3 plateau accompanying the spontaneous symmetry breaking of the translation, the cusp singularities above and/or below the plateau, and the even-odd effect in the magnetization curve.