Vacuum entanglement governs the bosonic character of magnons

TL;DR

This paper explores how the bosonic nature of magnons is influenced by the level of multipartite entanglement in the vacuum state, revealing that strong entanglement can alter their quantum statistics.

Contribution

It demonstrates that multipartite entanglement in the vacuum state governs the bosonic character of magnons, providing new insights into quantum statistics in many-body systems.

Findings

Strong multipartite entanglement suppresses bosonic behavior of magnons.

Analysis of ground states in Heisenberg and Ising models supports the theory.

Insights into the necessity of non-local transformations like Jordan-Wigner.

Abstract

It is well known that magnons, elementary excitations in a magnetic material, behave as bosons when their density is low. We study how the bosonic character of magnons is governed by the amount of a multipartite entanglement in the vacuum state on which magnons are excited. We show that if the multipartite entanglement is strong, magnons cease to be bosons. We also consider some examples, such as ground states of the Heisenberg ferromagnet and the transverse Ising model, the condensation of magnons, the one-way quantum computer, and Kitaev's toric code. Our result provides insights into the quantum statistics of elementary excitations in these models, and into the reason why a non-local transformation, such as the Jordan-Wigner transformation, is necessary for some many-body systems.