Fractional S^z excitation and its bound state around the 1/3 plateau of the S=1/2 Ising-like zigzag XXZ chain

TL;DR

This paper investigates the microscopic excitations around the 1/3 magnetization plateau in an Ising-like zigzag XXZ chain, revealing domain-wall particles and their bound states as key low-energy excitations.

Contribution

It introduces a microscopic analysis combining perturbation theory and Bethe-form wave functions to identify domain-wall particles and their bound states around the 1/3 plateau.

Findings

Domain-wall particles with S^z=±1/3 identified as low-energy excitations.

Bound states of domain-walls with S^z=±2/3 explain cusp singularities.

Microscopic mechanism for even-odd magnetization behavior elucidated.

Abstract

We present the microscopic view for the excitations around the 1/3 plateau state of the Ising-like zigzag XXZ chain. We analyze the low-energy excitations around the plateau with the degenerating perturbation theory from the Ising limit, combined with the Bethe-form wave function. We then find that the domain-wall particles carrying $S^z=\pm 1/3$ and its bound state of $S^z=\pm 2/3$ describe well the low-energy excitations around the 1/3 plateau state. The formation of the bound state of the domain-walls clearly provides the microscopic mechanism of the cusp singularities and the even-odd behavior in the magnetization curve.