Isotropic Spin Wave Theory of Short-Range Magnetic Order

TL;DR

This paper introduces an isotropic spin wave theory for short-range magnetic order in Heisenberg magnets, featuring three identical modes and providing analytical temperature-dependent thermodynamic predictions that align well with numerical data.

Contribution

It develops a novel isotropic spin wave theory with three modes, differing from conventional models, and applies it to analyze thermodynamics of antiferromagnets.

Findings

Good agreement with numerical results across broad temperature range

Analytical expressions for thermodynamic observables

Three-mode isotropic spin wave model successfully describes short-range order

Abstract

We present an isotropic spin wave (ISW) theory of short-range order in Heisenberg magnets, and apply it to square lattice S=1/2 and S=1 antiferromagnets. Our theory has three identical (isotropic) spin wave modes, whereas the conventional spin wave theory has two transverse and one longitudinal mode. We calculate temperature dependences of various thermodynamic observables analytically and find good (several per cent) agreement with independently obtained numerical results in a broad temperature range.