Electron spin resonance shifts in S=1 antiferromagnetic chains

TL;DR

This paper develops a theoretical framework using effective field theories to analyze ESR shifts in S=1 antiferromagnetic chains, achieving quantitative agreement with experimental data on NDMAP.

Contribution

It introduces a novel approach combining the O(3) nonlinear sigma model and free fermion theories to accurately describe ESR shifts near critical fields in spin-1 chains.

Findings

Quantitative agreement with ESR experiments on NDMAP.

Effective field theory captures magnon interactions and anisotropy effects.

Extension of the O(3) NLSM to near-critical field regimes.

Abstract

We discuss electron spin resonance (ESR) shifts in spin-1 Heisenberg antiferromagnetic chains with a weak single-ion anisotropy based on several effective field theories, the O(3) nonlinear sigma model (NLSM) in the Haldane phase, free fermion theories around the lower and the upper critical fields. In the O(3) NLSM, the single-ion anisotropy corresponds to a composite operator which creates two magnons at the same time and position. Therefore, even inside a parameter range where free magnon approximation is valid, we have to take interactions among magnons into account. Though the O(3) NLSM is only valid in the Haldane phase, an appropriate translation of Faddeev-Zamolodchikov operators of the O(3) NLSM to fermion operators enables one to treat ESR shifts near the lower critical field in a similar manner to discussions in Haldane phase. We present that our theory gives quantitative agreements with recent ESR experimental results on an spin-1 chain compounds NDMAP.