Ultrastrong coupling between a microwave resonator and antiferromagnetic resonances of rare earth ion spins

TL;DR

This paper demonstrates the first experimental ultrastrong coupling between a microwave resonator and antiferromagnetic resonances in a rare earth crystal, opening new avenues for quantum magnonic applications.

Contribution

It provides the first experimental evidence of ultrastrong coupling with antiferromagnetic resonances, expanding quantum magnonics beyond ferromagnetic systems.

Findings

First demonstration of ultrastrong coupling with antiferromagnetic magnons

Potential for novel quantum magnonic devices using rare earth materials

Enhanced robustness due to antiferromagnetic order

Abstract

Quantum magnonics is a new and active research field, leveraging the strong collective coupling between microwaves and magnetically ordered spin systems. To date work in quantum magnonics has focused on transition metals and almost entirely on ferromagnetic resonances in yttrium iron garnet (YIG). Antiferromagnetic systems have gained interest as they produce no stray field, and are therefore robust to magnetic perturbations and have narrow, shape independent resonant linewidths. Here we show the first experimental evidence of ultrastrong-coupling between a microwave cavity and collective antiferromagnetic resonances (magnons) in a rare earth crystal. The combination of the unique optical and spin properties of the rare earths and collective antiferromagnetic order paves the way for novel quantum magnonic applications.