Antiferromagnetic order without recourse to staggered fields

TL;DR

This paper explores how local decoherence, modeled as continuous measurement, can induce antiferromagnetic order without the need for an external staggered magnetic field, providing a new understanding of symmetry breaking in quantum magnets.

Contribution

It demonstrates that local decoherence can replace the traditional staggered field in establishing antiferromagnetic order, within a decoherence framework.

Findings

Local decoherence can induce symmetry-broken order similar to staggered fields.

Repeated local measurements can serve as an alternative to external fields in quantum magnetism.

Analysis of small magnetic systems shows the feasibility of this approach.

Abstract

In the theory of antiferromagnetism, the staggered field---an external magnetic field that alternates in sign on atomic length scales---is used to select the classical N\'eel state from a quantum magnet, but justification is missing. This work examines, within the decoherence framework, whether repeated $local$ measurement can replace a staggered field. Accordingly, the conditions under which local decoherence can be considered a continuous measurement are studied. The dynamics of a small magnetic system is analysed to illustrate that local decoherence can lead to (symmetry-broken) order similar to order resulting from a staggered field.