Exact Analysis of ESR Shift in the Spin-1/2 Heisenberg Antiferromagnetic Chain

TL;DR

This paper develops an exact perturbation theory for ESR shift in the spin-1/2 Heisenberg antiferromagnetic chain, revealing detailed temperature and magnetic field dependencies and highlighting deviations from classical predictions.

Contribution

It provides an exact analysis of the ESR shift using Bethe ansatz, covering all temperature and magnetic field ranges for the first time.

Findings

g-shift depends strongly on magnetic fields at low temperature

Exact results for resonance shift across temperature and field ranges

Asymptotic behavior characterized in the low-temperature limit

Abstract

A systematic perturbation theory is developed for the ESR shift and is applied to the spin-1/2 Heisenberg chain. Using the Bethe ansatz technique, we exactly analyze the resonance shift in the first order of perturbative expansion with respect to an anisotropic exchange interaction. Exact result for the whole range of temperature and magnetic field, as well as asymptotic behavior in the low-temperature limit are presented. The obtained g-shift strongly depends on magnetic fields at low temperature, showing a significant deviation from the previous classical result.