Diverging entanglement of critical magnons in easy-axis antiferromagnets

TL;DR

This paper explores how entanglement between magnons diverges at phase transitions in easy-axis antiferromagnets and extends this criticality to cavity magnonics, proposing photon measurements as a detection method.

Contribution

It uncovers the divergence of magnon entanglement at magnetic phase boundaries and links magnetic criticality to superradiant phase transitions in cavity magnonics.

Findings

Magnon entanglement diverges at phase boundaries.

Superradiant phase transition occurs in cavity magnonics.

Cavity photon measurements can detect magnetic phase transitions.

Abstract

We study the instability of antiferromagnets with easy-axis anisotropy under a magnetic field, uncovering single or even multiple phase transitions at the boundary between non-collinear and collinear spin orderings. Near the phase boundary, the entanglement between the sublattice magnons diverges due to the interplay among antiferromagnetic exchange interaction, anisotropy, and magnetic field. Furthermore, our study reveals that this magnetic criticality extends to a superradiant phase transition within cavity magnonics systems. The magnon-photon interaction results in diverging cavity photon numbers and squeezing in the ground state at the transition points between spin orderings. This investigation not only elucidates the criticality of multi-component squeezed magnons in antiferromagnets, but also proposes cavity photon measurements as a viable method for detecting magnetic phase transitions.