Infinite coupling magnon theory of quantum Heisenberg magnetic models of spin s

TL;DR

This paper introduces an infinite magnon coupling term into the Holstein-Primakoff transformation for quantum Heisenberg models, removing unphysical states and improving accuracy near transition temperatures.

Contribution

It proposes a novel infinite coupling approach that makes the magnon series expansion finite, enhancing the theoretical description of spin models.

Findings

Achieves better results than existing spin wave theories near transition temperatures.

Removes unphysical magnon states from the models.

Provides a more rigorous and finite series expansion of magnon operators.

Abstract

An infinity magnon coupling term is introduced into the Holstein-Primakoff transformed forms of the Heisenberg ferromagnetic and antiferromagnetic models of any spin $s$ to rigorously remove the unphysical magnon states. This term makes the series expansion of the square root of the magnon operators become a finite series of magnon operator products. Under a simple Hubbard-like approximation our infinite coupling theory yields much better result than the existing spin wave theories, especially near transition temperatures.