High cooperativity in coupled microwave resonator ferrimagnetic insulator hybrids

TL;DR

This paper demonstrates strong coupling between exchange-coupled spins in a ferrimagnetic insulator and a superconducting microwave resonator, highlighting potential for cavity QED and high-density spin system integration.

Contribution

It reports the first observation of high cooperativity in coupled microwave resonator ferrimagnetic insulator hybrids with exchange-coupled spins.

Findings

Coupling rate of 450 MHz exceeds the spin system loss rate of 50 MHz.

Coupling strength scales with the square root of the number of spins.

Exchange-coupled systems are suitable for cavity quantum electrodynamics experiments.

Abstract

We report the observation of strong coupling between the exchange-coupled spins in gallium-doped yttrium iron garnet and a superconducting coplanar microwave resonator made from Nb. The measured coupling rate of 450 MHz is proportional to the square-root of the number of exchange-coupled spins and well exceeds the loss rate of 50 MHz of the spin system. This demonstrates that exchange coupled systems are suitable for cavity quantum electrodynamics experiments, while allowing high integration densities due to their extraordinary high spin densities. Our results furthermore show, that experiments with multiple exchange-coupled spin systems interacting via a single resonator are within reach.