Tunable Cooperativity in Coupled Spin--Cavity Systems

TL;DR

This study demonstrates how the cooperativity in a spin--cavity system can be tuned via magnetic field changes, achieving a wide range of magnon-photon coupling strengths in a skyrmion host material.

Contribution

It provides the first experimental demonstration of tunable cooperativity in a coupled spin--cavity system using magnetic phase transitions.

Findings

Cooperativity can be tuned from 1 to 60 by magnetic field.

Dispersive coupling observed between resonator and magnon modes.

Results modeled with input-output formalism.

Abstract

We experimentally study the tunability of the cooperativity in coupled spin--cavity systems by changing the magnetic state of the spin system via an external control parameter. As model system, we use the skyrmion host material Cu$_2$OSeO$_3$ coupled to a microwave cavity resonator. In the different magnetic phases we measure a dispersive coupling between the resonator and the magnon modes and model our results by using the input--output formalism. Our results show a strong tunability of the normalized coupling rate by magnetic field, allowing us to change the magnon--photon cooperativity from 1 to 60 at the phase boundaries of the skyrmion lattice state.