Dynamical structure factors of the spin-1/2 XXX chain at finite magnetic field

TL;DR

This paper analyzes the dynamical structure factors of the spin-1/2 XXX chain under finite magnetic field, deriving exact exponents for singularities and discussing experimental implications for neutron scattering.

Contribution

It provides exact momentum and spin-density dependences of singularity exponents for the entire momentum range in the thermodynamic limit, highlighting the stability of these features against higher-order excitations.

Findings

Exact exponents for singularities in dynamical structure factors derived

Higher-order excitations do not alter the singularity exponents

Implications for neutron scattering experiments on spin-chain compounds

Abstract

We study the dynamical structure factors of the spin-1/2 XXX chain at finite magnetic field h, focusing in particular on the singularities at excitation energies in the vicinity of the lower thresholds of the leading-order dominant excitations. We derive the exact momentum and spin-density dependences of the exponents controlling the singularities for both the longitudinal and transversal dynamical structure factors for the whole momentum range, in the thermodynamic limit. In that limit we argue that the higher-order excitations change neither the exponents nor the sharpness of the singularities. We discuss the relation to neutron scattering and suggest new experiments on spin-chain compounds using a carefully oriented crystal.