High-Cooperativity Cavity QED with Magnons at Microwave Frequencies
High-Cooperativity Cavity QED with Magnons at Microwave Frequencies
Using a sub-millimetre sized YIG (Yttrium Iron Garnet) sphere mounted in a magnetic field-focusing cavity, we demonstrate an ultra-high cooperativity of $10^5$ between magnon and photon modes at millikelvin temperatures and microwave frequencies. The cavity is designed to act as a magnetic dipole by using a novel multiple-post approach, effectively …