The correlation length of the Heisenberg antiferromagnet with arbitrary spin S

TL;DR

This paper investigates the correlation length in the Heisenberg antiferromagnet for arbitrary spin S, revealing that non-magnon effects at large S cause deviations from effective field theory predictions, and provides corrected theoretical insights.

Contribution

It introduces a spin-wave expansion to account for non-magnon effects, improving the agreement between theory and experimental/numerical data for large S.

Findings

Corrected prediction aligns better with data

Non-magnon effects are significant at large S

Effective field theory limitations are identified

Abstract

Experiments and numerical data on the correlation length for large S disagree strongly with the theoretical prediction based on the effective field theory prescription of the magnon physics. The reason is that for large S, at any accessible correlation lengths, the cut-off effects from the non-magnon scales become large and can not be treated by an effective field theory. We study these effects in a spin-wave expansion. The corrected prediction connects the renormalized classical and the classical scaling regions smoothly and comes close to the data.