# Strong magnon-photon coupling in ferromagnet-superconducting resonator thin-film devices

## TL;DR

This paper reports the demonstration of strong magnon-photon coupling in a thin-film permalloy device on a superconducting resonator, with tunable coupling strength and enhanced nonlinear effects, advancing quantum magnonics and on-chip information transfer.

## Contribution

It introduces a novel thin-film ferromagnet-superconducting resonator system with tunable strong coupling and nonlinear enhancement, enabling future quantum hybrid devices.

## Key findings

- Coupling strength of 0.152 GHz achieved
- Coupling tunable by magnetic field rotation and permalloy volume
- Enhanced coupling observed in nonlinear regime due to flux vortices

## Abstract

We demonstrate strong magnon-photon coupling of a thin-film permalloy device fabricated on a coplanar superconducting resonator. A coupling strength of 0.152 GHz and a cooperativity of 68 are found for a 30-nm-thick permalloy stripe. The coupling strength is tunable by rotating the biasing magnetic field or changing the volume of permalloy. We also observe an enhancement of magnon-photon coupling in the nonlinear regime of the superconducting resonator, which is mediated by the nucleation of dynamic flux vortices. Our results demonstrate a critical step towards future integrated hybrid systems for quantum magnonics and on-chip coherent information transfer.